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About the Tool

The Heat Trends Explorer presents modeled temperature outputs from i-Tree Cool Air simulations for selected locations across New York State. Results compare a 10-year Historical period (2010–2019) with corresponding weather patterns simulated under a warmer Future climate (2050–2059). Additional information about the climate inputs is available in About the Thermodynamic Global Warming (TGW) Dataset.

Up to 16 counties, cities or towns, census tracts, or census block groups may be included in a project. Location and Overview provide climate, population, land-cover, and heat-vulnerability context for the selected areas. Temperature Thresholds summarizes days meeting a selected temperature; Heat Event Characteristics compares event intensity, duration, and frequency; and Hourly Temperature Graphs display temperature changes throughout individual heat events.

Results may be viewed as Air Temperature, Heat Index, or Wet Bulb Globe Temperature. Minimum, Mean, and Maximum represent the coolest location, area-weighted average, and hottest location within each area.

Heat Event Types

Four heat-event types are used to compare shorter daytime heat events and multi-day events with limited nighttime cooling.

Event Type	NYS Heat Advisory	NYS Heat Warning	National Heat Advisory	National Heat Warning
Maximum Heat Index Requirement	95-104.9°F 2+ hours	>=105°F 2+ hours*	100-104.9°F 2 or more consecutive days	>=105°F 2 or more consecutive days**
Minimum Air Temperature	--	--	75°F	75°F

* NYS Heat Warning total duration is calculated as >95°F.

** National Heat Warning total duration is calculated as >100°F Heat Index and >75°F air temperature.

How to Use the Tool

Location

Use the Location page to choose the places you want to investigate or compare. You can select up to 16 areas across multiple geography types, although only one geography layer is displayed on the map at a time.

Not sure where to start?

Begin with the question you want to explore:

Understand heat exposure in one place. Search for a familiar address or select a community, then review its climate, population, land-cover, and heat-vulnerability statistics.
Identify priority areas within a city or town. Load census tracts or block groups, use Box Select to select neighboring areas, and sort the tables to find places with higher temperatures, greater vulnerability, or less tree cover.
Compare places with similar characteristics. Use Overlays or Identify to find areas with similar populations, land cover, or Heat Vulnerability Index rankings. Select them to compare how their temperatures and heat events differ.
Explore how heat may change over time. Select one or more areas and continue to the results pages to compare historical and future heat intensity, duration, frequency, thresholds, and hourly temperature patterns.

Choose and select areas

Choose Counties, Cities/Towns, Census Tracts, or Census Block Groups from the Area Type dropdown. Areas from more than one geography type may be included in the same project. To reopen a previously saved project, choose Import Project (.uhip) from this dropdown.

Use the address search in the upper-left corner of the map to navigate to a place. After an area type loads:

Select is active by default. Click a boundary to add it to your project.
Identify lets you click a boundary and preview basic population and temperature information without selecting it.
Box Select lets you click and drag across the map to select several areas at once.

The active map tool is highlighted in green.

Use overlays to guide your selection

Open the Overlays tab to view additional information beneath or across the selectable boundaries. Available overlays include median temperature, land cover, community characteristics, Heat Vulnerability Index data, and a combined index representing heat vulnerability, exposure, and potential planting space.

Use the transparency control to reveal the basemap or layers underneath an overlay. Hover over an information icon to read the source and meaning of a layer. With Identify active, you can also query census-scale overlays for a particular boundary.

Review and refine selected areas

As you select areas, the tables beside the map populate with information that can help you decide which areas to keep:

Summary provides a quick comparison of population, Disadvantaged Community percentage, and average maximum air temperature.
Land Cover compares tree cover, impervious cover, and estimated plantable space.
Climate summarizes historical and future temperatures and heat-event occurrence.
Census describes populations that may be more vulnerable or exposed to extreme heat.
HVI presents Heat Vulnerability Index results for New York City and the rest of the state.

Percentiles compare each area with other areas of the same geography type across New York State. For example, a tract’s percentile is based on all tracts rather than on counties or cities.

Use the table controls to refine your selection:

centers the corresponding area on the map.
sorts a table by name or value.
explains a field or statistic.
removes an individual area from the project.

Use Clear all to remove every selected area. When you are satisfied with your selections, choose Continue to open the Overview page.

Overview

Use the Overview page to review your selected areas, prepare them for comparison, and decide which heat analysis best answers your question. Customizing the areas is optional: if you are exploring a single place or want a quick analysis, you can review the tables and continue directly to another results page.

Organize areas for comparison

The Area List shows each selected area with a default alias, color, and order. Order reflects the sequence in which the areas were selected and determines how they appear in subsequent tables, graphs, and legends.

Choose Edit to make changes:

Alias: Replace an area’s default name with a recognizable neighborhood, street, or community name. The alias will appear in tables and graph legends.
Color: Choose a color swatch to assign a color that will be used in the Area View map, tables, and graphs.
Order: Use the move up button and move down button to control the order in which areas appear.

Colors and order can be used to group areas by geography, temperature, vulnerability, or another characteristic. For example, related neighborhoods could share similar colors, or areas could be ordered from lower to higher temperature.

Use the icon beside an ID to center that area in the Area View map. Use the recenter map button to return the map to the full selection.

Choose Save to apply changes. To preserve the selected areas, aliases, colors, and order for another session, choose Export Project (.uhip). The saved project can later be reopened from the Location page.

Review and export the comparison tables

The Summary, Land Cover, Climate, Census, and HVI tables contain the same information available during Location selection, now with export controls. Use the sort icon in a column heading to rank areas by name or value.

Choose Export All CSV to download the tables and their data-key files in a ZIP folder. These files can be opened in spreadsheet software or joined to other data in GIS software using an area’s name or ID.

Choose Export All PNG to download shareable images of every table in a ZIP folder, together with a short description of the contents.

Not sure what to explore next?

Choose the results page that best matches your question:

Use Temperature Thresholds to find how often temperatures exceed a value such as 85°F or 90°F. Compare the warmest, coolest, and average conditions within each area to see whether heat is concentrated or widespread.
Use Heat Event Characteristics to compare the intensity, duration, and frequency of heat events and examine how those events may change in a warmer future climate.
Use Hourly Temperature Graphs to examine when daytime temperatures peak, how much areas cool overnight, how long hazardous conditions persist, and how air temperature, heat index, and wet bulb globe temperature differ during an event.

If you are still exploring, start with the Summary and Climate tables, then open the results page that corresponds to the largest difference or concern you observe.

Temperature Thresholds

Temperature Thresholds counts the days when a selected temperature measure exceeded a chosen value during each day’s warmest hour. The graphs begin with days above 85°F Mean Air Temperature and make it possible to compare areas, temperature measures, and Historical and Future modeled conditions.

Start with a question

If you are not sure where to begin, choose a setting based on what you want to learn:

What are conditions like across the area as a whole? Begin with Mean Air Temperature.
Are there notably cooler or localized hot spots? Compare Minimum and Maximum with Mean.
How does humidity affect experienced heat? Compare Heat Index with Air Temperature.
How often might outdoor activity involve direct-sun heat stress? Explore Wet Bulb Globe Temperature.
How could threshold exceedances change in a warmer climate? Compare Historical and Future counts.

Choose what the graph counts

The graph can be adjusted with three main settings:

Temperature Type: Choose Air Temperature, Heat Index, or Wet Bulb Globe Temperature (WBGT).
Warmest Hour Statistic: Choose Minimum, Mean, or Maximum to determine how temperatures within each selected area are summarized during the warmest hour of each day.
Temperature Threshold: Adjust the value in five-degree increments. Air Temperature and Heat Index range from 75–105°F; WBGT ranges from 75–95°F.

Raising the threshold isolates increasingly hot days, so counts can only decrease or remain the same. Lowering it includes more moderately hot days, so counts can only increase or remain the same. Higher thresholds can also make differences between otherwise similar areas easier to distinguish. Temperature statistics do not include pixels classified as open water.

Read the Historical and Future graphs

The graphs display Historical (2010s) and Future (2050s) results side by side, beginning with values summarized by modeled year. Each plotted value is a number of qualifying days, not a temperature.

Historical (2010s) results are modeled outputs from i-Tree Cool Air simulations based on the historical climate. These outputs are calibrated representations of long-term conditions, not day-for-day reconstructions of observed weather. Future (2050s) uses the same weather patterns adjusted to an SSP245 warmer climate. The comparison illustrates how the same conditions could produce a different number of days above the selected threshold; it is not a weather forecast.

Use the Legend control to show or hide selected areas. The Labels checkbox displays values on the graph, while Select All | None turns all areas on or off. Use + Expand Table to review the values currently displayed in the graph.

Use Minimum, Mean, and Maximum together

Minimum represents the lowest modeled temperature among pixels within the area during each day’s warmest hour.
Mean represents the area-weighted average across the selected geography during each day’s warmest hour.
Maximum represents the highest modeled temperature among pixels within the area during each day’s warmest hour.

Similar Minimum, Mean, and Maximum counts suggest that the selected area is relatively consistent at that threshold. A Minimum well below the Mean may point to cooler portions associated with tree cover, wetlands, elevation, or less impervious cover. A Maximum well above the Mean may reveal a localized hot spot even when the area’s average appears moderate.

Always consider geographic scale. A county or city mean can conceal meaningful variation among its neighborhoods, census tracts, or block groups.

Compare temperature types carefully

Air Temperature describes the modeled ambient temperature.
Heat Index describes how hot it feels when relative humidity is combined with air temperature.
Wet Bulb Globe Temperature describes heat stress in direct sunlight while accounting for temperature, humidity, wind speed, sun angle, and cloud cover.

The same numerical threshold does not represent an equivalent level of heat across these measures. For example, 85°F WBGT is not a degree-for-degree match for 85°F Air Temperature. More Heat Index days than Air Temperature days at the same threshold can show where humidity pushes experienced heat above that value. Fewer WBGT days at the same threshold do not indicate an absence of heat stress; WBGT uses a different scale, and meaningful heat stress can occur below the selected value.

Use the Heat Index Health Impacts graphic (opens in a new tab) and WBGT Health Impacts graphic (opens in a new tab) for context. Treat guidance values as decision-support references rather than a boundary between safe and unsafe conditions. WBGT guidance also varies by region and outdoor activity.

Explore yearly and monthly patterns

Select a graphed year to view its monthly breakdown. This can reveal whether the total is concentrated in a short period or distributed across the warmer season. Use the By Year link to return to the full decade view.

Compare more than one modeled year before treating a single high or low count as representative. The pattern across years and months provides more context for the frequency and seasonality of threshold exceedances.

Refine, investigate, and export

If a selected statistic has no qualifying days, lower the threshold or inspect another modeled year. A zero count at one threshold does not mean that the area experiences no heat exposure. If several areas have similar counts, raise the threshold or compare Minimum and Maximum to expose differences in their hottest conditions.

To locate the hot or cool pixels suggested by Minimum and Maximum results, examine an hourly map in the Extreme Heat Mapper (opens in a new tab). Use Export CSV to download the currently graphed data or Export PNG to download separate and composite images of the graphs and any expanded tables.

Heat Event Characteristics

Use the Heat Event Characteristics page to compare how hot, long-lasting, frequent, and widespread modeled heat events are—and how those characteristics may change in a warmer future climate. Results can be reviewed across the full 10-year Historical and Future periods or explored by year, month, and day.

Understand what is being compared

The Historical results are modeled outputs from i-Tree Cool Air simulations for 2010–2019 based on historical climate conditions. These outputs are calibrated representations of long-term conditions, not day-for-day reconstructions of observed weather.

The Future period applies a warmer 2050–2059 climate to the same weather patterns. This paired comparison helps show how similar conditions could produce hotter or longer events and how additional days could newly qualify as heat events. The results are modeled, not forecasts of when future events will occur.

The tool groups events into four categories:

NYS Heat Advisory: heat index greater than 95°F for at least two hours.
NYS Heat Warning: heat index greater than 105°F for at least two hours.
National Heat Advisory: maximum heat index greater than 100°F for at least two days, with minimum nighttime air temperature greater than 75°F.
National Heat Warning: maximum heat index greater than 105°F for at least two days, with minimum nighttime air temperature greater than 75°F.

These categories support consistent comparisons within the tool. They do not represent official advisories or warnings issued by National Weather Service offices or the criteria used by those offices.

Not sure where to start?

Begin with the question you want to answer:

Where is modeled heat most severe? Compare maximum intensity to identify the areas with the highest peak heat index.
Where do hazardous conditions persist longest? Compare average or summed duration to distinguish typically long events from the total amount of event time.
Where is heat most recurrent? Compare time-averaged or total frequency to identify repeated heat exposure.
Where might conditions change the most? Use the Difference view to find areas where events become hotter, longer, or more frequent in the Future modeled outputs.
What happened during a particular period? Select a year, month, and day to examine individual events, event types, duration, maximum heat index, and geographic reach.

Start with the decade summary

The Intensity / Duration / Frequency summary provides a quick comparison across selected areas and the Historical and Future 10-year periods. It includes all heat-event types and displays:

Maximum Intensity: the highest heat index reached during an event.
Average Duration: the average number of hours per event.
Total Frequency: the total number of events in the selected 10-year period.

Use this summary to identify which areas stand out before moving to the detailed graphs.

Use the Legend control to show or hide selected areas. The Labels checkbox displays values on the graph, while Select All | None turns all selected areas on or off. Use Export CSV to download the graphed data or Export PNG to download shareable images of the graph and legend.

Choose what to compare

The detailed heat-event graphs can be adjusted using four sets of controls:

Metric: Use Intensity, Duration, or Frequency to choose the characteristic shown on the graph.
Metric Type: Choose how that characteristic is summarized:
- For intensity, compare Average or Maximum heat index.
- For duration, compare Average hours per event or Sum of all event hours.
- For frequency, compare Time-averaged occurrence or Total event count.
Filter: Use Filter to include or exclude individual event types, such as displaying only heat warnings or only multi-day events.
View: Use the Decades / Difference switch to alternate between side-by-side Historical and Future results and the calculated difference between paired Historical and Future years.

Use the + Expand Table control to view the values currently displayed in the graph. Use the Legend control and its checkboxes to focus the graph on particular areas, show or hide labels, or clear and restore all selections. Use Export PNG to download separate and combined images of the graph and expanded table.

Move from decades to individual events

The detailed graphs begin with values summarized by year. Select a graphed year to display its monthly results. Select a month to generate daily event timelines beneath the monthly graph.

Use the By Years link to return from the monthly view to the full decade. Use Export Month CSV to download all Historical and Future event records for the selected month.

In the daily timelines:

represent NYS event categories that exceed a heat-index threshold for at least two hours.
represent National event categories that exceed a heat-index threshold for at least two days while remaining above the minimum nighttime air-temperature threshold.

Multi-day events may overlap single-day events because the same period can meet more than one event definition. Long-duration event bars are drawn over overlapping single-day bars. Use the Legend control to isolate particular event types.

Select a day to open a table of the events occurring on that date. The table includes:

Start: when the event first met its qualifying heat-index threshold.
End: when it stopped meeting the applicable heat-index or nighttime-temperature criteria.
Duration: the number of hours between the event’s start and end.
Block Group Count: for cities and counties, the number of census block groups within the area that met an event definition.
Maximum Heat Index: the highest modeled heat-index value reached during the event.

Use to close the table and clear the selected date.

Interpret the results

Use maximum and total metrics when you want to understand the greatest modeled burden:

Maximum intensity identifies the highest peak heat.
Sum duration identifies the greatest total amount of time spent in qualifying events.
Total frequency identifies the greatest number of events.

Use average metrics when you want to understand what a typical event was like. Interpret averages alongside their corresponding maximum or total. An average can decrease even when overall heat risk increases—for example, if the Future results contains many new, shorter events in addition to several extreme events. If an average change seems unexpected, switch to the corresponding Maximum, Sum, or Total metric.

In Difference view, positive values indicate an increase from the Historical results to the paired Future results. Look for more than a single large number: an area may experience higher peak heat, longer events, more events, or a shift from single-day to multi-day event criteria. Each pattern describes a different type of changing exposure.

For cities and counties, use Block Group Count to distinguish localized heat from widespread conditions. A larger area can meet multiple event definitions when some of its block groups remain hotter for longer than others. If the results vary substantially within a city or county, return to Location and analyze census tracts or block groups for a more detailed spatial comparison.

Areas with intense, persistent, frequent, or geographically widespread events may warrant closer consideration for cooling access, shade and tree planting, heat-safety outreach, emergency planning, or public-health messaging. Compare Heat Event Characteristics with the population, land-cover, and Heat Vulnerability Index tables before drawing conclusions about priorities.

Hourly Temperature Graphs

Use Hourly Temperature Graphs to examine how modeled temperatures change throughout an individual heat event. These graphs can help you identify when temperatures peak, how long high heat persists, how much an area cools overnight, and whether the hottest conditions are widespread or concentrated in part of an area.

The graph initially displays Maximum Heat Index for every selected area, with Historical and Future results shown together.

Not sure where to start?

Begin with the question you want to explore:

When does heat peak, and how long does it persist? Start with Maximum Heat Index and compare the timing and duration of the highest values.
How much does an area cool overnight? Select Air Temperature and pay particular attention to nighttime conditions during multi-day events.
Is heat widespread or concentrated? Compare Minimum, Mean, and Maximum. These statistics represent the coolest part, area-wide average, and hottest part of each selected area.
How does humidity affect experienced heat? Compare Air Temperature with Heat Index.
What might outdoor heat stress be like in direct sunlight? Select Wet Bulb Globe Temperature.
How might the same event change in a warmer climate? Compare the Historical and Future lines or select Difference to view the change at each hour.

Hourly Temperature Graphs are most useful for examining one event closely. Use Heat Event Characteristics when you want to compare intensity, duration, and frequency across an entire modeled 10-year period.

Choosing an Event

Select an event from the list on the left side of the page to generate an hourly graph. Two types of events are available:

Event Option	Local Events	Statewide Event
Coverage	Events shared by all selected areas	A fixed event shown for every selected area
Availability	Dates when every selected area meets heat-event criteria for at least four overlapping hours	June 29–July 5, 2018
Resolution	300-meter modeled temperature data	30-meter modeled temperature data
Best For	Examining heat events affecting the selected areas at the same time	Comparing areas when Local Events are limited or unavailable
Spatial Context	Represents the selected project areas	Uses the same event available in the Extreme Heat Mapper

Local Event eligibility is based on the modeled Future results. This allows the list to include weather patterns that did not produce qualifying heat in the modeled Historical results but become heat events under a warmer climate.

Each Local Event card displays its Historical start date, total overlapping event duration, and highest Maximum Heat Index. Events are initially arranged by date.

Use Sort by to arrange Local Events by date, duration, or Maximum Heat Index. Use Filter by to narrow the list by event length or Historical/Future year pairing.

The Statewide Event covers a longer period so users can examine heating and cooling patterns across New York. Because it spans a statewide period, not every date is necessarily an extreme-heat day in every selected area. Its higher-resolution data can be especially useful for comparing average conditions among areas or examining the same hours spatially in the Extreme Heat Mapper.

Why Local Events may be limited

Local Events require qualifying heat to overlap across every selected area. Widely separated areas, large geographies, and areas containing rural or high-elevation block groups are less likely to share many qualifying hours.

Hourly data also depend on geography:

Census Block Groups: The Statewide Event is displayed for the individual block group. Local Event data use the census tract containing that block group because of storage limitations. A block group may meet a heat-event definition without producing a Local Event if the full tract does not qualify.
Census Tracts: Local Events are stored when all block groups within the tract meet the applicable heat-event criteria.
Cities and Towns: Local Events are stored when all encompassing block groups meet the criteria. Municipal and census boundaries may not align closely, particularly in rural areas.
Counties: Local Events are stored when all block groups within the county meet the criteria.

If no Local Events appear, try selecting fewer areas, choosing smaller census geographies, or focusing on more urban locations. You can also use the Statewide Event to compare the existing selections.

Use to collapse or expand the event list when you want more room for the graph.

Hourly Temperature Graph Controls

After selecting an event, adjust the graph using three principal settings:

Temperature: Choose Air Temperature, Heat Index, or Wet Bulb Globe Temperature.
- Air Temperature is the modeled ambient temperature approximately six feet above the ground.
- Heat Index describes how hot conditions feel when relative humidity is combined with air temperature.
- Wet Bulb Globe Temperature (WBGT) describes heat stress during activity in direct sunlight while accounting for temperature, humidity, wind speed, sun angle, and cloud cover.
Statistic: Choose Minimum, Mean, or Maximum.
- Minimum represents the lowest modeled temperature among pixels within the geography at each hour.
- Mean represents the area-weighted average temperature across the geography.
- Maximum represents the highest modeled temperature among pixels within the geography at each hour.
Time: Choose which climate period or comparison to display.
- Historical (2010s) results are modeled outputs from i-Tree Cool Air simulations based on the historical climate. These outputs are calibrated representations of long-term conditions, not day-for-day reconstructions of observed weather.
- Future (2050s) uses corresponding weather patterns adjusted to an SSP245 warmer climate.
- Difference displays Future minus Historical for each corresponding hour. Because Difference values represent a change in temperature rather than an actual temperature, they cannot be displayed on the same axis as the Historical and Future series.

Historical and Future can be displayed separately or together. Turning one period off can make differences among selected areas easier to see.

Use Reset Graph to return to Maximum Heat Index with all selected areas enabled.

Use Legend to show or hide individual areas. If the graph contains many lines, use Select None and then enable one or two areas at a time. Use Select All to restore every area.

Interpret hourly patterns

represents modeled outputs from the Historical simulation. represents modeled outputs from the Future simulation. represents the hour-by-hour Future-minus-Historical change.

Follow each line from left to right to examine:

When daytime heating begins.
The hour when temperatures reach their peak.
How quickly temperatures fall after the peak.
Whether high temperatures persist into the evening.
How much the area cools overnight.
Whether temperatures remain elevated across multiple days.

Select a graphed hour to review the corresponding Historical and Future values. When comparing areas, look at both the highest value and the length of time temperatures remain elevated. Two areas may reach similar peaks while experiencing very different durations of high heat.

Difference is useful for identifying the hours and areas with the greatest modeled warming. A positive value means the Future temperature is higher than the corresponding Historical temperature. Compare Difference graphs across multiple events before concluding that one area will consistently experience the greatest change.

Compare Minimum, Mean, and Maximum

Minimum, Mean, and Maximum describe different parts of the same geography and should be interpreted together:

When all three remain close, heat is likely distributed broadly across the area.
When Maximum and Mean are similar but Minimum is noticeably lower, cooler pockets may be present.
When Minimum and Mean are similar but Maximum is noticeably higher, the most intense heat may be concentrated in a smaller hot spot.
When the statistics reach similar peaks but remain elevated for different lengths of time, heat may be widespread but more persistent in some parts of the area.

For a guided explanation of these distributions, open Page Guide and continue to the Hourly Temperature Graphs example. The Page Guide walks through Minimum, Mean, and Maximum using a selected area and explains what differences in peak temperature and duration can reveal about heat distribution.

For Heat Index, compare both peak temperature and the number of hours above 95°F. A Maximum series may meet the tool’s heat-event criteria even when Mean or Minimum does not. This indicates that qualifying heat was concentrated in the hottest part of the area. “No Qualifying Heat Event” for Mean or Minimum does not mean that the area experienced no heat-related risk.

Geographic scale matters. A county or city average can conceal substantial variation among its neighborhoods, tracts, or block groups. Use smaller geographies or the Extreme Heat Mapper to investigate possible hot or cool locations spatially.

Compare temperature measures

Air Temperature, Heat Index, and WBGT answer different questions and should not be compared as though their numerical values use the same risk scale.

Compare Air Temperature with Heat Index to understand the effect of humidity. When Heat Index is higher, humidity is increasing how hot the conditions feel. Similar values suggest humidity had a more limited effect during those hours.

Use Air Temperature to examine nighttime cooling. Remaining above 75°F overnight helps satisfy the nighttime condition used for National multi-day events in this tool. Nights above 70°F can still increase heat-related health strain even when the event does not meet that definition.

WBGT accounts for direct sunlight and wind in addition to temperature and humidity. It can rise or fall more sharply than Air Temperature or Heat Index as sunlight, clouds, or wind conditions change. Interpret WBGT using its own flag-based health guidance rather than comparing it degree-for-degree with the other measures.

Use the Human Health Considerations link to review the Heat Index or WBGT guidance associated with the selected temperature type. These guidance values provide context; falling below an event or warning threshold does not necessarily mean conditions are risk-free.

For multi-day events, consider the combination of daytime intensity and nighttime cooling. Repeated hot days can create greater health strain when temperatures remain elevated overnight.

Use related tools and export

Use the Extreme Heat Mapper (opens in a new tab) when you want to locate the hot or cool pixels suggested by Minimum and Maximum results or view selected Statewide Event hours spatially.

Compare multiple events before treating one temperature spike, warm night, or large Difference value as representative of an area. Use Heat Event Characteristics to determine whether similar patterns appear across the full modeled 10-year period.

Use Export CSV to download the currently graphed hourly values. Use Export PNG to download the graph and any applicable table content as images.

Graph Considerations

Keep these modeling and display details in mind when reading the graph:

Small one- or two-degree oscillations may result from changing cloud cover, which affects daytime solar heating and nighttime heat loss.
A sharp daytime increase followed by a rapid decrease may represent full-sun conditions before clouds or precipitation reduce incoming solar radiation.
A Future value may occasionally be below its corresponding Historical value. The Future simulation applies warmer-climate forcing to the Historical weather pattern, but cloud cover, precipitation, wind speed, and wind direction can still vary. Evaluate the event’s overall pattern rather than expecting every Future hour to be warmer.
WBGT may show larger hourly increases and decreases because it is particularly sensitive to sunlight and wind.
A selected area may only appear during part of the graph. Temperatures are stored for each area’s heat-event hours, together with two hours before and after. Different single-day events may overlap a multi-day event that defines the full displayed period.
An area or statistic may show “No Qualifying Heat Event.” This means the applicable temperature and duration requirements were not met. Temperatures can still be compared, and heat-related risk may still have been present below those thresholds.

Examples

These examples demonstrate how Heat Trends Explorer results can inform practical planning and implementation decisions. Each example follows one planning question from area selection through interpretation and shows how the resulting tables and graphs can support a plan, program, or operating procedure.

Example 1

Plan for Longer, Hotter Heat Events

This example follows a municipal planning team examining extreme heat for a local climate adaptation or heat action plan. The planning question is whether future risk in Niagara Falls is limited to higher peak temperatures or also includes longer events, more qualifying heat days, broader exposure across the city, and less evening or overnight relief.

The Temperature Thresholds, Heat Event Characteristics, and Hourly Temperature Graphs tabs are reviewed together to create a local heat-risk profile. The resulting evidence can inform assumptions about multi-day heat-response operations, cooling-center availability, and the timing and geographic reach of public-health outreach.

Identify Location(s)

First, use the Location tab to identify the part(s) of the state with the greatest modeled temperature increase. Select ‘Counties’ from the Area Type dropdown, then use Identify to click areas and view summary statistics.

The largest average temperature increases occur in western New York, particularly along the Great Lakes. Niagara Falls is selected for this example because it has an average maximum temperature increase of 4.6°F, more than a 6x increase in heat event days, over 45,000 residents, and 84% of residents classified as living in a disadvantaged community (DAC).

Within a planning process, these temperature, population, and DAC values establish the local hazard and vulnerability context. They can support the problem statement in a heat adaptation plan and document why Niagara Falls warrants more detailed neighborhood-level assessment.

In the Overview tab, the selected layer color and display name can be customized. The project and the Land Cover, Climate, Census, and HVI table tabs can also be exported from this pane.

Identify results for Niagara Falls. — With Identify active, click a layer on the map to view total population, DAC percentage, and average maximum temperature.

Temperature Thresholds

The tool tracks air temperature, heat index, and wet bulb globe temperature (WBGT). WBGT combines air temperature, humidity, wind, and solar radiation to estimate heat stress. For each temperature type, the tool summarizes the daily maximum using three statistics:

Minimum: the daily maximum temperature reached at the coolest pixel within the selected area. This often represents high tree cover and low impervious cover and helps identify whether any outdoor relief from high temperatures exists within the area.
Mean: the area-averaged value across all block groups for the maximum-temperature hour. This is best for understanding average heat exposure across the selected area.
Maximum: the daily maximum temperature reached at the hottest pixel within the selected area. This often represents low tree cover and high impervious cover and helps identify the highest potential heat exposure in the area.

Because Niagara Falls is close to the Great Lakes, humidity can make the heat index higher than the air temperature. Comparing minimum, mean, and maximum values helps explain how the hottest days affect both the full city and its most extreme locations.

The default graph shows a notable increase between modeled outputs for the Historical and 2050s periods. It counts days when the citywide average heat index is above 85°F at the hottest hour of the day, including forested areas within the city boundary.

The threshold graphs show the following patterns:

Minimum heat index above 90 degrees Fahrenheit.

On the hottest historical days, the minimum heat index at the hottest hour was rarely above 90°F. When it did exceed 90°F, the mean heat index was usually above 95°F. In the 2050s replay, the minimum heat index exceeds 90°F on up to 8 days per year.

Average maximum heat index above 95 degrees Fahrenheit.

In the modeled Historical results, some years had only one day with an average maximum heat index above 95°F. In the 2050s replay, multiple days exceed that threshold each year.

Maximum heat index above 100 degrees Fahrenheit.

In the modeled Historical results, only one day had a maximum heat index above 100°F. In the 2050s replay, every year has at least one such day, and hotter years have more than a week of days with maximum heat index above 100°F.

To analyze seasonal timing, move year by year to identify early-season (May) and late-season (September) high temperatures, which can be important because people may be less acclimated at the beginning and end of the warm season.

Annual counts above selected thresholds can serve as measurable indicators in a local heat plan. They describe how often widespread or concentrated heat occurs, whether high-heat days are becoming routine, and whether preparedness activities may need to begin earlier or continue later in the warm season.

Heat Event Characteristics

The Heat Event Characteristics tab summarizes modeled outputs for four heat event types across the 10-year Historical simulation and 10-year 2050s replay. The thresholds use heat index, which combines air temperature and humidity to estimate how hot conditions feel to the human body:

Event Type	NYS Heat Advisory	NYS Heat Warning	National Heat Advisory	National Heat Warning
Heat Event Threshold	>95°F Heat Index2+ hours	>105°F Heat Index2+ hours	>100°F max Heat Index2+ days and minimum air temperature >75°F	>105°F max Heat Index2+ days and minimum air temperature >75°F

Below the Intensity/Duration/Frequency summary, the tool shows heat events by year. By default, the graph displays the maximum heat index reached by any event in the selected timeframe. The controls can switch to average heat index, or to total and average duration and frequency metrics.

Duration shows how much longer heat events become in the 2050s replay. Increases can come from the same historical event lasting longer or from weather patterns that did not produce extreme events in the modeled Historical results but cross advisory or warning thresholds in the 2050s replay.

Frequency shows how many additional events cross a heat threshold. In some years, Niagara Falls has up to 10 times as many events in the 2050s replay; years with no historical events can also gain multiple heat event days.

Use to filter event types. For example, filtering to National events shows that no historical events met the multi-day National Heat Advisory or Warning criteria. This suggests that the historical events were single-day events with enough nighttime cooling to avoid multi-day classifications.

Filtered heat event frequency for Niagara Falls. — Niagara Falls total event frequency filtered to show only National (multi-day) heat events.

Clicking any year shows the monthly breakdown. In this example, 2016 is selected because it has the greatest number of historical events.

The monthly breakdown shows no modeled heat events in June for either the Historical results or the 2050s replay. May and September each double in total events, July increases 7x, and August increases 4x while still having the largest total number of events. Clicking a date in August opens the daily breakdown for that event.

Historical and future monthly heat events for Niagara Falls. — Historical and 2050s replay comparison for August 2016/2056 in Niagara Falls. There were 4 events in the Historical results and 17 events (+13) in the 2050s replay.

Daily historical and future heat event tables. — Historical (left) and 2050s replay (right) events for August 10, 2016/2056.

The daily table shows that:

The historical heat wave had 8 hours above 95°F heat index in Niagara Falls, affecting 20 of the city’s 58 block groups. The highest heat index across any block group was 96.5°F, indicating that roughly half of the city experienced high afternoon heat-index values.

The 2050s replay varies across the city:

Thirty block groups experienced a multi-day National Heat Advisory, with a maximum heat index of 110.8°F. Although this value is above the National Heat Warning threshold, the Warning requires every day in the event to exceed 105°F heat index; at least one day in this grouping was above 100°F but below 105°F.
Twenty-four block groups experienced a NYS Heat Advisory, defined as 2 or more hours above 95°F heat index. The highest labeled heat-index value was 105.9°F, meaning at least one block group briefly exceeded the NYS Heat Warning threshold but did not remain above it long enough to qualify as a Warning.
The remaining four block groups met the tool's NYS Heat Warning criteria, defined as 2 or more hours above 105°F heat index, with event duration measured from the period above 95°F heat index. These block groups experienced at least 2 hours above 105°F and sustained heat-index exposure above 95°F from 9 AM to 9 PM.

These results show three spatial heat patterns. The urban core reaches heat-index values up to 110.8°F and has limited nighttime cooling between two high-heat days. A transition zone also reaches high daytime heat index but can cool below 75°F overnight, providing some physiological relief. The remaining block groups still experience moderately high daytime heat, but at lower intensity than the 34 block groups in the higher-risk zones.

This section shows how the Heat Event Characteristics tab can move from a broad decade-level comparison into a specific event-day interpretation. For Niagara Falls, the August 10 comparison shows that the 2050s replay is not just hotter; it also changes the type, duration, and spatial extent of heat risk. A historical afternoon heat event affecting part of the city becomes a future event where all block groups meet some heat event threshold, with the urban core differentiated as experiencing the highest heat index values and limited nighttime cooling. This aids in understanding whether future heat risk is driven by higher intensity, longer duration, more frequent events, broader exposure across the city, or a combination of all four.

For a local heat adaptation plan, the August 10 comparison represents a practical planning scenario: a short event affecting part of the city becomes a multi-day event affecting every block group. This supports testing whether heat-response services can remain active across consecutive days while directing additional outreach toward the urban core.

To view how events are distributed within a city, select a smaller geography, such as census tracts, in addition to the city. See the third example for a detailed tract-scale analysis.

Hourly Temperature Graphs

The Hourly Temperature Graphs tab can display the 8-day Statewide Heat Event at 30-meter resolution or the 16 local events generated for Niagara Falls. A local event is included when the full city crosses a heat event threshold at some point in the 2050s replay, whether it is a single-day NYS Heat Advisory or a multi-day National Heat Advisory. For each event hour, the Modeled outputs for the Historical and 2050s periods can be plotted for minimum, mean, and maximum values. Sorting by maximum heat index identifies August 13, 2016, as the hottest historical event.

The maximum heat index within the city increases from 102.74°F in the modeled Historical results to 113.09°F in the 2050s replay. The hotter climate also pushes the 95°F heat-index threshold 2 hours earlier and keeps the heat index above 90°F until after sunset; historically, temperatures were already falling below 90°F by 5 PM.

Maximum hourly heat index graph for Niagara Falls.

The minimum heat index increases by up to 10.7°F at the maximum hour, meaning the entire city reaches at least NYS Heat Advisory conditions. At individual hours, differences reach up to 22°F: where the modeled Historical results show citywide cooling by 5 PM because of a cold front or precipitation, the 2050s replay retains heat farther into the evening under different moisture and weather conditions.

Minimum hourly heat index graph for Niagara Falls.

Earlier threshold crossings and reduced evening relief provide operating information that annual totals cannot show. These hourly patterns can inform the daily timing of cooling services, public-health messaging, and other heat-response activities.

Planning Application

Taken together, the results support a Niagara Falls heat adaptation plan that accounts for a shift from localized afternoon heat to broader, longer events with less evening and overnight relief. The threshold graphs show how frequently important conditions occur, decade summaries document the overall heat-event change, and hourly graphs identify when exposure begins and how long it persists. These outputs can form a local heat-risk profile used to establish multi-day response assumptions and target neighborhood outreach.

Example 2

Prioritize Communities for Heat-Resilience Support

This example follows a regional or state planning program comparing communities for heat-resilience funding or technical assistance. The planning task requires a consistent method for comparing places with similar population and vulnerability characteristics while recognizing that the highest current heat and the greatest future increase may occur in different locations.

Census tracts are selected using common criteria and evaluated through climate, land-cover, threshold, heat-event, and hourly results. The exported tables can provide a documented screening record, while the detailed graphs help verify which communities warrant further local assessment.

Identify Locations

In the Location tab, census tracts provide the best comparison scale for this example. They are small enough to identify areas with similar population size, but large enough to support tract-level hourly temperature graphs. Block groups are not ideal here because hourly graphs are aggregated to tract values.

Across the state, select at least one tract from each region with a population above 3,000 and a high temperature relative to nearby tracts. In upstate cities with multiple tracts near 3,000 residents, select the tract with the highest average temperature. In and near New York City, most tracts have more than 4,000 residents, so the selected tracts may not represent the hottest parts of all five boroughs.

Identify results for statewide tract selection. — With Identify active, click a layer to view a population and temperature summary.

Overview

In total, 11 census tracts were chosen to represent the state, including two in New York City. Each tract has between 3,000 and 4,000 people and is designated as a disadvantaged community with a moderate-to-high Heat Vulnerability Index (HVI).

Use the Overview tab to rename each census tract, adjust colors, and reorder selections. In this example, tracts are sorted north to south and west to east; they could also be sorted by HVI, temperature, or another table statistic. The Overview tab can also export the selections and customized appearance for later use.

The tables below the Area View & List can be exported as images or CSV files. The Land Cover tab reports average tree cover and impervious cover. Plantable space is calculated as total tract area minus impervious cover and tree cover, and can serve as a rough screening estimate for green interventions or other projects.

The shared population, DAC, and HVI criteria create a repeatable comparison group. Renaming, ordering, and exporting the selections produces a clear review package that can accompany a funding or technical-assistance screening memo.

Temperature Tables

Annual heat event changes table. — Increases in Annual NYS (single-day) Heat Events and National (multi-day, limited nighttime cooling) Heat Events.

The Climate tab reports the median maximum air temperature for June through September in the Historical and 2050s timeframes. Simulations were conducted using i-Tree Cool Air with the thermodynamic global warming (TGW) dataset. The resulting modeled outputs show how historical weather patterns can change in intensity and duration under a hotter climate with different moisture and related weather behavior. Because the method replays historical weather patterns rather than creating new weather sequences, frequency changes represent events that were previously non-severe crossing heat thresholds in the 2050s replay.

The Heat Advisories & Warnings section breaks down the annual count of NYS single-day events and the total count of National multi-day events. Absolute change should be considered alongside baseline event counts. New York City has the highest increase in both event types, but also starts with the highest baseline event count. Average NYS single-day events roughly double, and National multi-day events roughly quadruple. Rochester has the largest single-day increase, with a 5.6x rise in annual average events. Brookhaven has the largest National-event jump among areas with historical National days, increasing 12x, largely because high overnight lows on Long Island can support multi-day events.

Temperature Thresholds

The threshold graphs can be viewed for air temperature, heat index, and wet bulb globe temperature (WBGT). WBGT combines air temperature, humidity, wind, and solar radiation to estimate heat stress. For each temperature type, the tool summarizes the daily maximum using three statistics:

Minimum: the daily maximum temperature reached at the coolest pixel within the selected area. This helps identify whether any outdoor heat relief exists in the area.
Mean: the area-averaged value across the selected tract for the maximum-temperature hour. This is best for understanding average exposure across the tract.
Maximum: the daily maximum temperature reached at the hottest pixel in the selected area. This is best for identifying the highest potential heat exposure.

The tool loads with 85°F mean heat index by default, which provides a broad overview of heat occurrences in each area. Adjusting the statistics reveals different patterns:

Mean: New York City and Yonkers have the highest counts in both time periods, consistent with their minimum and maximum rankings. Albany, Binghamton, Newburgh, and Syracuse follow. Brookhaven appears to have the highest percent increase because it has low historical counts, but future values are closer to other areas.

Minimum: New York City, and to a lesser extent Yonkers, have nearly identical mean and minimum day counts, suggesting uniform urban development across the selected tracts.

Maximum: Brookhaven is no longer the lowest outlier, while Buffalo and Rochester rank lower than they do for minimum or mean temperature. Plattsburgh remains lower than Albany for minimum and mean, but is similar to Albany for maximum temperature.

Changing the temperature type and threshold can reveal additional high- and low-temperature patterns. Heat index and WBGT also include Human Health Considerations that help interpret the danger of different thresholds. Examples include:

Maximum air temperature threshold chart.

Air temperature (maximum): New York City has the highest counts of maximum temperatures above 90°F, but the 2050s replay shows parts of Plattsburgh, Albany, and Syracuse reaching values similar to Crown Heights and Tremont in New York City.

Mean heat index above 105 degrees Fahrenheit.

Heat index (mean): Human Health Considerations indicate that heat index above 103°F can make heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure or physical activity. Days above 105°F mean heat index increase substantially for New York City in the 2050s replay. Buffalo, Brookhaven, and Binghamton have the fewest days above 105°F mean heat index at the hottest hour.

WBGT (mean): Human Health Considerations split New York into two regions. The highest threat level begins at 84°F for Rochester, Buffalo, Plattsburgh, and Long Island, and at 87.6°F for the rest of the state. A mean WBGT of 85°F is reached at least one historical day per year in most locations and in all locations in the 2050s replay. Albany has notably higher WBGT than cities with similar heat index and air temperature, such as Plattsburgh and Syracuse, and in some years surpasses Yonkers as the third-highest WBGT location.

Threshold results show whether exposure is widespread or concentrated within each tract. These findings provide supporting evidence for why a community advances from statewide screening to local project development.

Heat Event Characteristics

The Heat Event Characteristics tab summarizes modeled outputs for four event types across the 10-year Historical simulation and 10-year 2050s replay. The thresholds use heat index, which combines air temperature and humidity to estimate how hot conditions feel to the human body:

Event Type	NYS Heat Advisory	NYS Heat Warning	National Heat Advisory	National Heat Warning
Heat Event Threshold	>95°F Heat Index2+ hours	>105°F Heat Index2+ hours	>100°F max Heat Index2+ days and minimum air temperature >75°F	>105°F max Heat Index2+ days and minimum air temperature >75°F

The Intensity/Duration/Frequency summary card focuses on three metrics:

Intensity, duration, and frequency summary chart.

Intensity, duration, and frequency metrics from the summary card.

Intensity: the maximum heat index reached across any event in the modeled outputs for the Historical or 2050s period. The highest intensities are in New York City, followed by Albany, Plattsburgh, and Syracuse.
Duration: the average length of all events. The highest average durations are in Newburgh and Brookhaven, while the greatest percent increases occur in Buffalo and New York City.
Frequency: the total count of events. Event counts generally follow the intensity pattern: New York City is highest, followed by Yonkers, Albany, Plattsburgh, and Syracuse. The largest percent increases occur in western New York, including Buffalo (+1069%, from 13 to 139 events) and Rochester (+674%, from 34 to 229 events).

Name	% Event Change
Plattsburgh	379%
Albany	340%
Rochester	674%
Syracuse	466%
Buffalo	1069%
Binghamton	484%
Newburgh	372%
Yonkers	269%
Tremont [BX]	227%
Crown Heights [BK]	221%
Brookhaven	443%

Absolute values and percentage changes answer different planning questions. High baseline values identify communities with substantial existing exposure, while large increases identify places where adaptation needs may grow rapidly. Reviewing both prevents prioritization from being based on a single ranking.

Below the summary card, the tool shows heat events by year. By default, the graph displays the maximum heat index from any event in the selected timeframe. The top controls can change the metric, metric type (average or sum), and graph view.

For this use case, switch to the Difference view. This replaces the side-by-side 2010s/2050s view with one 10-year graph showing the difference between decades, which is easier to read when many areas are selected. To compare absolute values, such as the location with the highest heat index, switch back to the Decades view. Use this section to examine intensity, duration, and frequency in more detail.

Intensity: How hot does it get?

Maximum

Maximum intensity shows where the highest heat-index values increase the most, based on the highest heat index from any event in the timeframe. Newburgh, Albany, Syracuse, Rochester, and Crown Heights in New York City each have high outliers in at least one year. Differences are not shown for selections that did not have historical data.

Difference in maximum heat index. — Difference in Maximum Heat Index across historical and 2050s heat events; outliers in Albany (orange), Newburgh (pink), Rochester (green), Crown Heights in NYC (light blue), and Syracuse (red).

Average

Average intensity shows how much the average event’s maximum heat index increased. Areas with many historical heat events often show consistently high increases because they have a larger sample of events that intensify in the 2050s replay, plus new events that did not meet a heat threshold historically. New York City and Yonkers are examples of areas with positive values in all years.

This statistic can be negative when the historical sample size is small. For example, Binghamton rarely reached 95°F heat index historically, but when it did, some events were multiple degrees hotter. In July 2019, Binghamton had two events with an average maximum heat index above 105°F. In the 2050s replay, the same month has fourteen events.

Use the Decades view and Select All | Select None to isolate Binghamton. This shows how the average intensity can decline even when heat risk increases: the frequency rises sharply because many additional, somewhat less intense events enter the dataset.

Binghamton average intensity example. — Heat events for Binghamton in July 2019/2059. The two 2019 events increase in intensity and duration in the 2050s replay, but the addition of many more events lowers the average maximum heat index.

Duration: How long are heat events?

Sum

The total duration increases substantially across the selected locations. Outliers appear in Plattsburgh, Newburgh, Brookhaven, and New York City. In Difference view, large outliers such as Plattsburgh should be inspected before assuming a simple increase in heat event severity.

Difference in total heat event hours. — Difference in total heat event hours across each year in the two decades.

The large 2053 Plattsburgh duration increase is largely traced to July. In July, Plattsburgh increased from five single-day NYS Heat events in 2013 to twelve events in 2053.

Plattsburgh July duration comparison. — Heat events for Plattsburgh in July 2013/2053.

Clicking a mid-July day with a National Heat Warning reveals why total hours increase so sharply. Plattsburgh has a long, continuous heat event, but its four block groups are varied enough that they fall under two different event classifications, which further inflates the total duration metric. The table shows three block groups with heat index above 100°F on each event day and minimum air temperature above 75°F. One block group has maximum heat index above 105°F for the final four days, meeting the National Heat Warning threshold. Both long events are included in the duration sum. The duration increase is still meaningful, but the total value is misleading because overlapping events within the tract are counted together.

Future heat events showing overlapping types. — Future heat events for July 19, 2053; note the multiple event types for Plattsburgh and Rochester that correspond with different block groups.

Average

Average duration shows how the typical event length changes. This statistic can be exaggerated in areas with few historical events, especially when those events were multi-day events or long single-day events. Newburgh shows a negative average difference in total hours for 2051 and 2059; after filtering to single-day events, most areas show an increase in average hours above 95°F heat index.

Average duration filtered for single-day events. — Average duration filtered for single-day heat events.

Frequency: How many events occurred?

Total

The total frequency difference shows how many more events occur in the 2050s replay. This is not always the same as event severity: for example, three separate NYS Heat Advisories can become one consecutive National Heat Advisory or Warning when days above 100°F heat index and nights above 75°F air temperature connect into a multi-day event. Even with this caveat, all areas see increases in total events, with the largest increases in Rochester, Yonkers, and New York City. Because Rochester has a high value compared with nearby Buffalo and Syracuse, inspect 2058 to verify whether event increases occur across multiple months. Although at least two overlapping events occur, the large Rochester increase is mostly confirmed by reviewing the year: historical counts are low, future counts are higher, and the Difference display remains larger for Rochester than for its nearby comparison cities.

Average

Average frequency shows the change in average events by year or month. Two types of outliers can appear. The first is a verifiable area with a large percent increase in events across the year. The second occurs when an area has few or no historical heat events, making future differences look unusually large. Brookhaven in 2016/2056 is an example of the second case. New York City locations show little change in that same year because most hot days already qualified as heat events; their duration or intensity changed instead.

This example shows how to compare many locations without relying on a single metric. Statewide comparisons identify where intensity, duration, and frequency increase, but the details matter: New York City and Yonkers may have high baseline heat exposure and high absolute values, while places such as Buffalo, Rochester, Brookhaven, and Plattsburgh show larger percent increases in future heat event frequency or duration. The example also shows why large changes should be inspected carefully: a high total-duration increase may reflect overlapping event types within a tract, while a negative average-intensity difference may occur when many new, lower-intensity events are added to a small historical sample. The Difference view, event filters, year/month/day drilldowns, and hourly graphs help separate real risk patterns.

This detailed review acts as a validation step before a community is placed on a priority list. It distinguishes sustained patterns from values driven by a low historical baseline, overlapping event classifications, or one exceptional modeled year.

Hourly Temperature Graphs

Hourly temperature graphs work best when one or only a few selections are shown. Local events represent periods when all selected tracts had a heat event, and the event length is determined by the longest overlapping heat event.

Sorting by Duration (shortest to longest), the shortest event is 10 hours long and occurs late in the summer on September 2, 2010. The graphs use the same temperature and statistic options as the threshold graphs: minimum, mean, and maximum. By default, they load with the maximum heat index, defined as the maximum value from any point in the selected tract. Clicking an hour in the graph populates the table below with historical, 2050s, and difference values. To narrow the graph to the areas with the largest differences, sort the Difference column from largest to smallest. For this event, Buffalo and Plattsburgh consistently show the largest maximum heat-index differences across hours.

Hourly graph sorting example. — September 2, 2010 heat event showing all areas. Clicking the graph populates an hourly table below it, allowing values to be sorted.

All areas can be removed from the graph using the Legend’s Select None option. Then re-check Buffalo and Plattsburgh to show only those plots, making the changes in event duration and intensity easier to interpret.

Buffalo’s modeled Historical results (solid purple) did not qualify for a heat event. The day was likely overcast, given the consistent temperatures throughout the day. In the 2050s replay (dash-dot purple), the tract experiences an 8-hour NYS Heat Advisory, with maximum heat index above 95°F. Afternoon warming suggests less overcast conditions, further increasing the difference from the Historical results. The maximum shifts from 88.45°F at 12 PM historically to 101.21°F at 6 PM in the 2050s replay.

Plattsburgh's modeled Historical results (solid blue) show a short NYS Heat Advisory that ended in the early afternoon with the arrival of overcast conditions or precipitation. In the 2050s replay (dash-dot blue), heat index above 95°F begins 2 hours earlier, the tract crosses the NYS Heat Warning threshold with more than 2 hours above 105°F heat index, and the cloud or precipitation pattern no longer cools the tract enough to end the heat event.

Filtered hourly temperature graph. — Filtered Hourly Temperature Graph for Plattsburgh and Buffalo only.

The same comparison can be repeated across temperature types and statistics to compare the hottest, coolest, and area-average conditions within each tract.

For mean WBGT, Plattsburgh’s historical and 2050s peak-temperature hours align. Although the hottest pixel’s heat index changes by more than 8°F, the mean WBGT across Plattsburgh is similar at the hottest hour. The 2050s replay, however, shows less relief from dangerous WBGT levels. Buffalo’s historical and 2050s mean WBGT values are closer together, around 5°F apart, than its maximum heat-index change, which is sometimes more than 10°F. However, Buffalo spends more time in the Red Flag WBGT zone than Plattsburgh, indicating more dangerous outdoor conditions in the 2050s replay of the same historical event.

The minimum WBGT changes less than the maximum or mean WBGT between modeled outputs from the Historical and Future simulations. It also reveals the urban character of the selected tracts: Buffalo has a minimum WBGT close to, and sometimes higher than, Plattsburgh. This aligns with Buffalo’s higher impervious cover, lower tree cover, lower latitude, and likely clearer conditions, given its steady temperature rise and fall compared with Plattsburgh’s pronounced 2 PM drop.

Hourly results show how shortlisted communities differ in the timing and duration of selected events, providing an additional check before final priorities are established.

Planning Application

This comparison provides a transparent method for developing a heat-resilience priority list. Communities with high existing exposure may require immediate support, while communities with large future increases may require earlier adaptation planning. The exported tables document the screening criteria and results, and the event-level review provides a quality-control step before funding, technical assistance, or local engagement decisions are made.

Example 3

Plan Safer Outdoor Work and Recreation

This example follows municipal public-health and parks staff preparing heat-safety procedures for outdoor employees, recreation programs, and public activities in East New York–City Line. The planning question is not limited to which tract is hottest; it also considers whether heat stress is widespread, whether cooler locations remain available, and when dangerous conditions begin and end.

WBGT overlays and tract rankings identify areas for closer review. The Temperature Thresholds tab shows how often different levels of heat stress occur, while the Hourly Temperature Graphs tab shows the time of day and duration of hazardous conditions.

Identify Locations with Overlays

This example focuses on wet bulb globe temperature (WBGT), a heat-stress metric that combines air temperature, humidity, wind, and solar radiation. To find high-WBGT areas, open the Location tab and use the median temperature maps in the Overlays tab. These maps show air temperature, heat index (air temperature combined with humidity), and WBGT at the block group scale, grouped into five color classes for each temperature type.

Median max WBGT map and legend. — Median Max WBGT map and legend shown during selection in the Location tab.

Climate Table

Among areas that qualify as disadvantaged communities, East New York–City Line in Brooklyn has the highest wet bulb globe temperature. Select the city to define the neighborhood boundary, then change the Area Type dropdown to Census Tracts. Use Box Select to select all tracts within the bounding city. Then use Average Maximum Temperature (June–September), filtered to WBGT, to sort and identify the hottest historical and 2050s census tract in the area. The average maximum temperature represents the median of daily maximum values for the hottest spot in each area.

Sorted median maximum WBGT table. — Median Maximum WBGT filtered in the top highlight and sorted by 2050s temperature value.

In the Overview tab, use the WBGT ranking in the Climate tab to adjust the Color and Order columns in the Area List. In this example, tracts use a rainbow sequence from red to green to purple, while the citywide selection is gray. This color scheme immediately reveals a spatial pattern in the Area View: the highest-ranked tracts, shown in red and orange, are mostly concentrated in the northeast, while the center of the neighborhood has lower average WBGT than the north or south ends.

Overview colors for East New York tracts. — Area View for each tract, colored according to maximum WBGT ranking.

The Overlays tab and the Climate tab provide an initial screening of program and service areas. Tracts with high WBGT rankings can be prioritized for facility review, additional shade assessment, or closer examination of outdoor activity locations.

Temperature Thresholds

Because this example focuses on WBGT, open the Temperature Thresholds tab and select Wet Bulb Globe Temperature. Brooklyn is in Region 2 in the Human Health Considerations graphic, so use the following WBGT flag categories:

Flag	Green	Yellow	Orange	Red	Black
Temperature	<75.9°F	75.9-78.7°F	78.7-83.7°F	83.7-87.6°F	>87.6°F
Threat	Low	Elevated	Moderate	High	Extreme

Mean

The threshold values in the tool increase in 5°F increments, such as 75°F, 80°F, and 85°F. These values do not align exactly with the flag thresholds, but they provide a practical way to assess the level of precaution needed. After switching the temperature type to WBGT, the statistics default to mean values above 85°F.

The mean temperature statistic represents the average temperature across the full area for the maximum heat hour. The gray bar represents the East New York neighborhood selection, which averages temperatures in proportion to the total area across all encompassed tracts. The highest-ranked dark-red tract has the most historical and 2050s days when the entire tract has WBGT above 85°F.

As we increase the temperature threshold, it can become easier to separate out the hottest years and areas with the most extreme heat.

Mean WBGT above 85 degrees Fahrenheit. — Mean WBGT >85°F; the highest-ranked tract (dark red), followed by tracts ranked #4–6 (orange/yellow), has the highest day counts.

Mean WBGT above 90 degrees Fahrenheit. — Mean WBGT >90°F; the pattern largely follows the 85°F threshold results.

Maximum

Maximum WBGT shows the hottest point in each area. Because the East New York neighborhood contains all selected census tracts, its day count is equal to or higher than the highest individual tract. For days when the hottest point in a tract reaches WBGT above 85°F, tracts ranked #3 (light red) and #7 (light yellow) equal or exceed the #1 tract in some years. This means the #1 tract has the highest average WBGT, but parts of other tracts can reach equal or higher hotspot temperatures.

Increasing the maximum WBGT threshold to 90°F makes the #1 tract more similar to other high-WBGT tracts. Although tracts #3 and #7 can have more Red Flag days, tract #1 has the highest incidence of Extreme, or Black Flag, WBGT. This indicates that tract #1 is most vulnerable to the most extreme WBGT values, while parts of other tracts can equal or exceed it on Red Flag days.

Maximum WBGT above 90 degrees Fahrenheit. — Max WBGT >90°F. The #1-ranked tract (dark red) is equaled or surpassed by parts of other tracts.

Minimum

Minimum WBGT shows the coolest point in each area. This helps identify whether an area has outdoor heat relief, often associated with high tree canopy. Because the East New York neighborhood contains all selected census tracts, its minimum value will match or be lower than the lowest individual tract.

Tracts ranked #4–6 (orange/yellow) have notably higher minimum WBGT than tract #1 in historical and 2050s years. Cross-comparing minimum, mean, and maximum values shows that tract #6 has similar counts across all three statistics for most years, indicating highly uniform WBGT stress across the tract. Several lower-ranked tracts, such as #10, also have minimum values equal to or higher than the top three WBGT tracts.

Minimum WBGT above 85 degrees Fahrenheit. — Min WBGT >85°F. Tracts #4–6 have the highest counts of days with high minimum WBGT; those counts often match their mean and maximum counts at the same threshold.

These threshold results show that tract #1 ranks highest mainly because of its high mean WBGT and its highest maximum WBGT above 90°F, or Black Flag days. Tracts #2 and #3 can contain hotspots that are hotter than tract #1 on Red Flag days, but their mean values are lower because higher tree cover creates lower minimum WBGT within the tracts. Tracts #4–6 show more uniform heat stress: when one part of the tract is above 90°F WBGT, much of the tract is likely above that threshold as well.

Lower-ranked tracts have lower mean WBGT, but can still experience maximums or minimums that are similar to or higher than the #1 tract. Use the Hourly Temperature Graphs tab to explore these WBGT patterns over time. To view spatial maps of Wet Bulb Globe Temperature, use the Extreme Heat Mapper.

The three statistics support different parts of an outdoor heat-safety procedure. Mean WBGT indicates how often broad area-wide precautions may be needed, Maximum WBGT identifies potential hot spots requiring site-level review, and Minimum WBGT indicates whether cooler outdoor relief may remain available. The number of Red or Black Flag days can inform seasonal staffing, training, shade, hydration, and supply planning.

Hourly Temperature Graphs

Hourly temperature graphs work best with one or only a few selections shown. Local events represent periods when all selected tracts have a heat event, and event length is determined by the longest overlapping heat event. Sorting by Max Heat Index (highest to lowest) places the most extreme events at the top. Among the top six events, the fifth-highest event has the highest future WBGT, surpassing 99°F, even though it ranks fifth by future maximum heat index at 122.92°F.

The maximum WBGT graph shows three immediate findings:

Historically, the first three days of this event were Black Flag days, and the fourth was a Red Flag day.
In the 2050s replay, all four days are Black Flag days, with an average WBGT increase of 4-6°F.
There is little heat-stress relief in the 2050s replay on the evening of July 19, and in both the modeled Historical and 2050s results on July 20–21.

Historical and 2050s time series can be toggled off in the Time section of Graph Options. The Difference graph can also be enabled to isolate the 2050s minus historical temperature difference by area and hour.

Maximum WBGT difference graph. — Max WBGT difference graph, with the highest hour selected on the graph. The hourly table is sorted by Difference from largest to smallest.

For the remaining graphs, four selections are isolated to study the area temperatures: the #1 ranked WBGT tract (dark red), the #5 WBGT tract (yellow) with very close minimum, mean, and maximum threshold counts, the lowest rank WBGT tract (purple), and the full East New York neighborhood (gray).

Mean WBGT generally follows the tract rankings, with the full East New York selection falling between the individual tracts. Some hours differ by only 0.2°F across all areas, but most daytime hours show mean differences of 1-2°F. The warmest WBGT tract usually has the largest WBGT increase in the 2050s replay.

Mean WBGT graph for selected tracts. — Mean WBGT temperature for three selected tracts and the East New York–City Line neighborhood (gray).

Minimum WBGT is much lower for the full East New York selection because it inherits the lowest WBGT value across all selected tracts. This low minimum helps show how the 2050s replay increases heat event severity: the coolest area in East New York–City Line shifts from historical Orange Flag conditions to Red and Black Flag conditions. Areas that may have been hot but tolerable for brief outdoor activity in the modeled Historical results would not be safe for prolonged exposure in the 2050s replay.

The minimum graph also validates the threshold findings. The #5-ranked tract (yellow) has a higher minimum WBGT than the #1-ranked tract, suggesting lower minimum tree cover and higher minimum impervious cover. The highest- and lowest-ranked tracts have similar minimum temperatures; even where maximum and mean values differ, every selected tract in East New York faces dangerous heat stress during the event.

Minimum WBGT graph for selected tracts. — Minimum WBGT temperature for three selected tracts and the East New York–City Line neighborhood (gray).

Hourly results translate the thresholds into operating times. The beginning, peak, and end of dangerous WBGT conditions can inform schedule changes, work-rest practices, movement of activities indoors, and decisions to postpone or cancel outdoor programs.

Planning Application

These results can support an outdoor heat-safety procedure that identifies priority tracts, establishes WBGT-based action levels, and defines the hours when protective measures are most likely to be needed. Threshold graphs describe the seasonal frequency of hazardous conditions, while hourly graphs support day-of-event scheduling and operating decisions. The analysis also distinguishes locations with isolated hot spots from areas where high heat stress is widespread and outdoor relief is limited.

Sources

Data

Simulations

The i-Tree Cool Air model (revision 1946) was simulated for January 1, 2010 through December 31, 2019 and January 1, 2050 through December 31, 2059 at 300-meter resolution. The simulations use 2019 land cover, tree canopy, and impervious cover inputs from the National Land Cover Database (NLCD). Elevation, in centimeters, was retrieved from the National Hydrography Dataset Plus V2 (NHDPlusV2). Simulations were divided by HUC10 watersheds to calibrate initial soil moisture and watershed discharge for each period.

Anthropogenic heat, or thermal energy released into the atmosphere from human activities, is represented using a 1-kilometer hourly anthropogenic heat flux dataset. Link The dataset provides anthropogenic heat emissions in W/m2 for each hour of the day across each month. The 1-kilometer grids are first averaged across all hours to create a 1-kilometer annual-average raster. Watershed-specific ratios are then used to convert the annual average to monthly values, with hourly ratios applied within each month.

The 1-kilometer anthropogenic heat grids are separated into commercial and residential emissions and transportation emissions. These components are resampled from 1-kilometer to 300-meter grid cells using impervious cover and urban land use distribution.

For November through April, the model was simulated in six-hour timesteps to capture daily minimum and maximum statistics while maintaining continuity in the water and energy balance across the simulation duration. For May through October, the model was simulated for all 24 hours in each day. Statistics are calculated for each 300-meter cell, water cells are removed, and cell statistics are aggregated to the census block group level.

Temperature Thresholds

Temperature thresholds provide a quick way to compare the daily maximum (the hottest hour) air temperature, heat index, and wet bulb globe temperature between years and areas. Temperature thresholds are calculated at every 5°F interval above 75°F.

The daily maximum can be displayed for the minimum pixel value (i.e., a high tree cover pixel), the mean of all pixels (area-weighted average of all mean block group temperatures), and maximum value (i.e., high impervious cover pixel).

Heat Event Characteristics

Heat events provide graphs for exploring the intensity, duration, and frequency of historical extreme heat events and their behavior under a warmer future climate. These graphs support comparisons of how long populations are exposed to dangerous heat, how extreme the heat is, and how often similar events occur.

Event statistics are calculated at the census block group level. Events are then aggregated to tracts, cities/towns, and counties based on block group overlap for tracts and counties, or majority overlap for cities/towns.

City/town populations across the state, but particularly in rural areas, have boundaries that do not align with tracts or block groups. Each block group is assigned to the city/town boundary with which it has the largest area overlap. All statistics for these incongruous areas are estimates.

The NYS and National Heat Advisory and Warning categories are used in this tool to classify and compare simulated heat events. Their definitions are not intended to represent official advisories or warnings issued by National Weather Service (NWS) Weather Forecast Offices, or the criteria those offices use. They support analysis of two broad patterns: shorter-duration, primarily daytime heat events (NYS) and multi-day heat events with limited nighttime cooling (National). Within each group, Advisory and Warning categories distinguish different heat-index thresholds.

There are four calculated event types:

NYS Heat Advisory: Qualifies when the maximum heat index from any pixel is greater than 95°F for two or more hours. Duration is calculated from the time any pixel is above 95°F heat index.
NYS Heat Warning: Qualifies when the maximum heat index from any pixel is greater than 105°F for two or more hours. Duration is calculated from the time any pixel is above 95°F heat index, so the full hazardous heat period is represented.
National Heat Advisory: Qualifies when the maximum heat index from any pixel is greater than 100°F for two consecutive days and at least one pixel has air temperature greater than 75°F during the event period. This event represents both daytime heat index and nighttime air temperature. Duration begins when any pixel exceeds 100°F heat index and continues until the event no longer meets the heat-index or air-temperature continuation criteria.
National Heat Warning: Qualifies when the maximum heat index from any pixel exceeds the warning threshold during a qualifying National heat event. Duration begins at the National Advisory start temperature of 100°F heat index, so the full hazardous heat period is represented and continues until the event no longer meets the heat-index or air-temperature continuation criteria.

To aggregate events from block groups to tracts, cities/towns, or counties:

Graph and statistics: When multiple block groups have an event for a single day or series of days, the aggregated geography inherits the earliest event start time, latest event end time, highest warning type, and maximum heat index from the series.
- The Intensity, Duration, and Frequency values shown in tables are determined by this inherited event count, regardless of how many block groups within the area qualified for a heat event.
Tables: The daily temperature tables accessed in the monthly graph show a detailed breakdown of block groups by event type and duration.
- If all block groups within an area meet any heat event criteria during the event, it is available as a graphable event in Hourly Temperature Graphs when all other selected areas also have an overlapping, full-coverage event.

Hourly Temperature Graphs

Hourly time series are available from both a fixed statewide time series and from local events where all queried areas meet a heat event criterion in the future scenario. This data provides a closer look at how temperature changes over the course of an event, rather than only summarizing intensity, duration, and frequency. Graphs are labeled with heat event and human comfort thresholds, including wet bulb globe temperature (WBGT), to support analysis of dangerous heat exposure by hour.

Statewide

Statewide time series are shown for June 29, 2018 through July 5, 2018. This high heat event was simulated at a neighborhood-level (30-meter) scale, containing ten times more detail than the multi-decade, 300-meter simulations used by the Local Events.

High-elevation and rural areas of New York rarely meet the heat event criterion of heat index greater than 95°F. As more areas with sparse events are compared, the probability that all selected areas have overlapping local events decreases. The long-duration statewide event allows comparison over multiple summer days regardless of whether every selected area reaches local maximum heat thresholds.

Additionally, block group-level hourly temperature values are available for the statewide event. For local events, block group temperatures are aggregated to the census tract scale.

Local

Local events are generated when every block group within the selected areas has an overlapping heat event. Each area has stored statistics for the minimum, mean, and maximum temperature for each hour of a heat event, as well as for the two hours before and after the heat threshold is met.

Census block groups are aggregated to the tract level for graph statistics to reduce space and memory requirements. To see block group details, the Heat Event Characteristics tab provides more detailed block group statistics for event duration and maximum heat index.

Map

Boundaries

Census Block Group: Administrative boundary data displaying the 2020 block group boundaries. Block groups are clusters of blocks within the same census tract and generally contain between 600 and 3,000 people. Link

Census Tract: Administrative boundary data displaying the 2020 census tract boundaries. Census tracts are subdivisions of United States counties and generally contain between 1,200 and 8,000 people, with an optimum size of about 4,000 people. Link

City/Town:

Non-NYC: Administrative boundary data displaying the 2020 county subdivision boundaries clipped to the shorelines of major hydrographic features. Census county subdivisions are divisions of counties, including Minor Civil Divisions (MCDs) and Census County Divisions (CCDs). Link
NYC: Administrative boundary data displaying the 2020 Neighborhood Tabulation Areas (NTAs). NTAs are created by aggregating census tracts within Community District Tabulation Areas (CDTAs). Link

County: Administrative boundary displaying the 2020 county boundaries clipped to the shorelines of major hydrographic features. Counties are the primary legal, administrative, and statistical subdivisions of a state. Link

Disadvantaged Communities: Administrative census tract-level boundary displaying disadvantaged communities (DACs) defined by the New York State Energy Research and Development Authority (NYSERDA). DACs are underserved communities identified as priority areas in planning and programs for state climate initiatives. Link

Economic Development Regions: Administrative boundary delineating New York into 10 separate regions based on shared economic interests, geography, and labor market. The Regional Economic Development Councils (REDCs) drive local, bottom-up economic growth and direct state investments. Link

State: Administrative boundary displaying the 2020 New York State boundaries clipped to the shorelines of major hydrographic features. Link

Overlays

Temperature

Air Temperature: Block group calculations for the 50th percentile of daily maximum air temperature from June through September for simulated years 2010–2019 at 300-meter resolution.

Heat Index: Block group calculations for the 50th percentile of daily maximum heat index from June through September for simulated years 2010–2019 at 300-meter resolution.

Wet Bulb Globe Temperature: Block group calculations for the 50th percentile of daily maximum wet bulb globe temperature from June through September for simulated years 2010–2019 at 300-meter resolution.

Land Cover

Tree Canopy: Tree canopy raster from the 2019 National Land Cover Database (NLCD) at 30-meter resolution, produced by the Forest Service as a partner in the Multi-Resolution Land Characteristics Consortium (MRLC). This layer represents the percentage of each cell occupied by the tree canopy. Link

Plantable Space: Estimated percentage of each cell that is not occupied by tree canopy or impervious cover. It is calculated as 100% minus tree canopy cover minus impervious cover. Because NLCD tree canopy cover can underestimate the existing canopy, this value may overestimate available planting space. Plantable space should therefore be interpreted as a screening-level indicator of potential planting opportunity rather than a field-verified estimate of plantable land. Supporting references: Nowak and Greenfield 2010 Link; Greenfield and Schleeweis 2019 Link

Impervious Cover: Impervious cover raster from the 2019 National Land Cover Database (NLCD) at 30-meter resolution, produced by the U.S. Geological Survey (USGS) Land Cover program. Link

Land Cover: Land cover raster from the 2019 National Land Cover Database (NLCD) at 30-meter resolution, produced by the U.S. Geological Survey (USGS) Land Cover program. It classifies land into categories including urbanization, forest, agriculture, grasslands, and wetlands. Link

Community

% POC: Percentage of the total population that is Hispanic or non-white, calculated at the block group level. Link

% Low Income: Percentage of the total population below 200% of the 2022 poverty level. Poverty threshold source: Link ACS table source: Link

% Disabled: Percentage of the total population with one or more disabilities, calculated at the census tract level. Link

% Elderly: Percentage of the total population over age 64, calculated at the block group level. Link

Heat Vulnerability Index (NY): Percentile score from 0 to 100 defined on a statewide, non-NYC census tract scale. The census tract HVI scores reflect how temperatures in the tract compare to temperatures in other areas of the state, how emergency department visits and hospitalizations for select heat-related health outcomes in the tract compare to other areas of the state, and characteristics of the population in the tract that may be linked with increased vulnerability to heat. Link

Heat Vulnerability Index (NYC): Score from 1–5 defined for Neighborhood Tabulation Areas (NTAs) in New York City. The index weighs air conditioning and green space access, median income, and Black/African American population. Link

Base Map

Map data copyrighted OpenStreetMap contributors and available from OpenStreetMap. Link

Tables

Summary

Disadvantaged Communities: Percentage of the population, based on census tracts, defined as living in a disadvantaged community (DAC) by NYSERDA. DACs are underserved communities identified as priority areas in planning and programs for state climate initiatives. Link

Total Population: Population summed from census block groups using the 2022 American Community Survey. Table B01003. Link

Avg. Max Air Temp (2010s): 50th percentile of daily maximum air temperature from June through September in simulated years 2010–2019.

Avg. Max Air Temp (2050s): 50th percentile of daily maximum air temperature from June through September in simulated years 2050–2059.

Land

Average values of land use characteristics from the 2019 National Land Cover Database (NLCD) used in model simulations.

Tree Cover %: Average tree cover percentage from 2019 NLCD Tree Canopy Cover. Link

Impervious Cover %: Average impervious cover percentage from 2019 NLCD Impervious Cover. Link

Plantable Space %: Estimated space remaining after subtracting tree canopy cover and impervious cover from total land area. This value is best interpreted as a screening-level estimate of potential planting opportunity. Tree canopy source: Link Impervious cover source: Link

Climate

Statistics from the 300-meter 2010–2019 and 2050–2059 simulations examining differences in heat between decades.

Average Maximum Temperature

Air Temperature	Heat Index	Wet Bulb Globe Temperature
50th percentile of daily maximum air temperature from June through September for the simulated decade.	50th percentile of the daily maximum heat index from June through September for the simulated decade.	50th percentile of daily maximum wet bulb globe temperature from June through September for the simulated decade.

Heat Advisories and Warnings

Annual NYS Heat Event Days	Total National Event Days
Average yearly number of days in the simulated decade where the maximum heat index is greater than 95°F for two or more hours. To read more about event calculations, see the Heat Trends About page. Because this value is calculated from maximum heat index, a city or county inherits an event any time one or more block groups within it meet the threshold.	Decadal sum of events where maximum heat index is greater than 100°F and nighttime air temperature is greater than 75°F for at least two days. To read more about event calculations, see the Heat Trends About page. Because this value is calculated from maximum heat index and warm overnight air temperature, a tract, city, or county inherits an event any time one or more block group within it meets the thresholds.

Annual NYS Heat Event Days

Total National Event Days

Average yearly number of days in the simulated decade where the maximum heat index is greater than 95°F for two or more hours. To read more about event calculations, see the Heat Trends About page.

Because this value is calculated from maximum heat index, a city or county inherits an event any time one or more block groups within it meet the threshold.

Decadal sum of events where maximum heat index is greater than 100°F and nighttime air temperature is greater than 75°F for at least two days. To read more about event calculations, see the Heat Trends About page.

Because this value is calculated from maximum heat index and warm overnight air temperature, a tract, city, or county inherits an event any time one or more block group within it meets the thresholds.

Census

Statistics for population from the 2018-2022 American Community Survey. The selected statistics represent populations that may be more vulnerable or exposed to extreme heat.

All variables except disadvantaged communities (DACs) are calculated at the census block group level and summed to all other geographies. City/town populations across the state have boundaries that do not align with tracts or block groups. Each block group is assigned to the city/town boundary with which it has the largest area overlap; therefore, population statistics for these areas are estimates.

Additionally, cities such as Syracuse, Rochester, Schenectady, and Plattsburgh have small geometries that do not encompass a full census block group boundary. If the additional geometry encompasses more than 50% of the area, it is included in the city population count.

Population: Total population from ACS 2018–2022. Table DP05. Link

% Disadvantaged Community: Percentage of the population identified as living in a disadvantaged community by NYSERDA. DACs are underserved communities identified as priority areas in planning and programs for state climate initiatives. This variable is calculated at the census tract scale. Link

% POC: Percentage of the total population that is Hispanic or non-white.

% Disabled: Percentage of the total population with one or more disabilities.

% Elderly: Percentage of the total population over age 64.

% No HS (25+): Percentage of the total population over age 25 with no high school diploma.

Heat Vulnerability Index (non-NYC)

The New York State Heat Vulnerability Index (HVI) is a percentile score from 0-100 defined on a statewide, non-NYC census tract scale. The census tract HVI scores reflect how temperatures in the tract compare to temperatures in other areas of the state, how emergency department visits and hospitalizations for select heat-related health outcomes in the tract compare to other areas of the state, and characteristics of the population in the tract that may be linked with increased vulnerability to heat. Link

The methodology for calculating the HVI can be found on the NYS Department of Health Website.

Heat Vulnerability Index and exposure, sociodemographics, and health outcome values are displayed as a median and min-max range for larger geographies with multiple census tracts, and as a single value for census tracts and block groups. All individual attributes for each category are visible as either a statewide percentile from 0–100 or as a raw value.

City/town populations across the state have boundaries that do not align with tracts. Each tract is assigned to the city/town boundary with which it has the largest area overlap; therefore, statistics for these areas are estimates and marked with a warning.

Heat Exposure Percentile: Percentile for summed heat exposure variables.

Exposure Variable	Description
Days >85°F Heat Index (HI) Trend	Yearly linear trend in the number of days the heat index reaches 85°F or greater since 2000.
Avg. Max Heat Index (HI)	Average daily maximum heat index for all landmass census tracts in New York State, excluding New York City, between May and September for years 2012–2021.

Sociodemographic Percentile: Percentile for summed sociodemographic variables.

Sociodemographic Variable	Description
% Black/AA	Percentage of the census tract population who are Black or African American Alone or in Combination with Some Other Race.
% Disabled	Percentage of census tract population with a disability.
% Elderly Live Alone	Percentage of census tract population age 65 years and older who live alone.
% Low Income	The percentage of the census tract population living below 200% of the poverty line.
% Limited English	Percentage of the census tract population age 5 and over who speak English less than very well.
% Outdoor Workers	Percentage of the employed civilian workforce in agriculture, forestry, fishing and hunting, mining, or construction industries.
% Uninsured	Percentage of the civilian non-institutionalized population without health insurance.

Health Outcome Percentile: Percentile for summed health outcome variables.

Values are rates per 100,000 people for aggregated subcounty areas. Percentiles are a statewide ranking for subcounty areas in New York State excluding NYC.

Health Outcome Variable	Description
Asthma Emergency Department (ED) Rate	Rate of asthma ED visits per 100,000 people.
Chronic Obstructive Pulmonary Disease Emergency Department Rate (COPD ED)	Rate of COPD ED visits per 100,000 people.
Heart Attack Emergency Department (ED) Rate	Rate of hospitalizations for heart attacks per 100,000 people.
Diabetes Hospitalization (HP) Rate	Rate of hospitalizations for diabetes per 100,000 people.
Acute Kidney Failure Emergency Department (ED) Rate	Rate of acute kidney failure ED visits per 100,000 people.

Heat Vulnerability Index: Heat Vulnerability Index from 0–100. This is the percentile of summed scores for heat exposure, sociodemographic, and health outcome factors, used to measure a census tract population's susceptibility to injury or harm during periods of hot weather.

Heat Vulnerability Index (NYC)

The New York City Heat Vulnerability Index is calculated at the Neighborhood Tabulation Area (NTA) scale and ranks neighborhoods from 1–5 based on environmental and social factors associated with increased heat risk. Since the HVI variables are calculated at the neighborhood scale, variables such as green space are not shown in this tool to avoid confusion with census block group or tract estimates such as tree cover percentage. View all HVI variables from the source. Link

Air Conditioning: Percentage of adults reporting that they have an air conditioner. Citywide median is 91%.

Median Income: Median household income at the neighborhood scale. Citywide median is $67,046.

Black Population %: Percentage of population identifying as Black or African American Alone or in Combination with Some Other Race.

Heat Vulnerability Index (HVI 1–5): Heat Vulnerability Index from 1–5, ranking NYC neighborhoods based on temperature, air conditioning, green space, median income, and racial inequalities.

Choose an area type from the dropdown, then select up to 16 areas on the map to compare simulated past and future heat exposures.
With an area type active, enable Identify to view basic information about an area, or enable Box Select to select several areas.
Launch the Page Guide or view the About tab in a new tab for help using the tool and to view examples.

Selected Areas

Select areas to populate the table.

ID	Total Population	DAC %	Avg. Max Air Temp (2010s)	Avg. Max Air Temp (2050s)	Clear

Land Characteristics

Average value of land use characteristics from the 2019 National Land Cover Database (NLCD) used in model simulations.

ID	Tree Cover % (Percentile)	Impervious Cover % (Percentile)	Plantable Space % (Percentile)

Climate Statistics

Statistics from the 300-meter 2010-2019 & 2050-2059 simulations examining differences in heat between decades.

Average Maximum Temperature (June–September)

Table Temperatures:

Air Temperature Heat Index WBGT

ID	Air Temperature (Percentile)			Heat Index (Percentile)			Wet Bulb Globe Temperature (WBGT) (Percentile)
ID	2010s	2050s	Change	2010s	2050s	Change	2010s	2050s	Change

Heat Advisories & Warnings

NYS Heat Events are days where the heat index is above 95°F for two or more hours. National Heat Events are multi-day events with a maximum heat index >100°F and a daily minimum air temperature >75°F. These definitions are for comparing simulated heat events and do not represent official National Weather Service alerts or local alert criteria. View days above an alternate temperature (i.e., 85°F) in the Temperature Thresholds tab.

View more details in Heat Event Characteristics.

ID	Annual NYS Heat Event Days (Percentile)			Total National Heat Event Days (Percentile)
ID	2010s	2050s	Change	2010s	2050s	Change

Census Data (ACS 2022)

Statistics for the population from the 2018-2022 American Community Survey. Statistics chosen are meant to represent populations more vulnerable or exposed to extreme heat.

ID	Population	% DAC	% POC (Percentile)	% Low-Income (Percentile)	% Disabled (Percentile)	% Elderly (Percentile)	% No HS (25+) (Percentile)

HVI (NYC)

The New York City heat vulnerability index is on the neighborhood tabulation (NTA) scale, ranking neighborhoods from 1–5 based on environmental and social factors associated with increased heat risk.

ID	Air Conditioning (Difference from Avg.)	Median Income (Difference from Avg.)	% Black	HVI (1-5)

HVI (non-NYC)

Heat Vulnerability Index from 0–100. This is the percentile of summed scores for heat exposure, sociodemographic, and health outcome factors, used to measure a census tract population's susceptibility to injury or harm during periods of hot weather.

ID	Heat Exposure Percentile	Sociodemographic Percentile	Health Outcome Percentile	Heat Vulnerability Index (HVI)

+ Expand Detailed Table

HVI Heat Exposure Indexes

Exposure is measured by the days >85°F heat index and the average maximum heat index (2012–2021) to rank areas by the number of days when negative effects of heat are elevated.

ID	Days >85°F HI Trend (+)	Avg. Max HI (°F)

HVI Sociodemographic Indexes

The sociodemographic index measures the ability of the population to adapt to instances of high temperature.

ID	% Black/AA	% Disabled	% Elderly Live Alone	% Low Income	% Limited English	% Outdoor Work

HVI Health Outcome Indexes

Health outcomes seek to track physiological vulnerability to health outcomes known to be exacerbated by high temperatures. Data is from aggregated subcounty areas. Values are rates per 100,000 people for aggregated subcounty areas. Percentiles are a statewide ranking for subcounty areas in New York State excluding NYC.

ID	Asthma ED Rate	COPD ED Rate	Heart Attack ED Rate	Diabetes HP Rate	Acute Kidney Failure ED Rate

Key: ED = Emergency Department Visit / HP = Hospitalizations

Customize, edit, and save selections below.
Move across the tabs above to interact with modeled heat-trend outputs.

Area View

Area List

ID	Name	Alias	Color	Order

ID	Name	Total Population	DAC %	Avg. Max Air Temp (2010s)	Avg. Max Air Temp (2050s)

Land Characteristics

Average value of land use characteristics from the 2019 National Land Cover Database (NLCD) used in model simulations.

ID	Alias	Tree Cover % (Percentile)	Impervious Cover % (Percentile)	Plantable Space % (Percentile)

Climate Statistics

Modeled statistics from the 300-meter i-Tree Cool Air simulations for 2010–2019 and 2050–2059, examining differences in heat between decades.

Average Maximum Temperature (June–September)

Table Temperatures:

Air Temperature Heat Index WBGT

ID	Alias	Air Temperature (Percentile)			Heat Index (Percentile)			Wet Bulb Globe Temperature (WBGT) (Percentile)
ID	Alias	2010s	2050s	Change	2010s	2050s	Change	2010s	2050s	Change

Heat Advisories & Warnings

ID	Alias	Annual NYS Heat Event Days (Percentile)			Total National Heat Event Days (Percentile)
ID	Alias	2010s	2050s	Change	2010s	2050s	Change

Census Data (ACS 2022)

Statistics for the population from the 2018-2022 American Community Survey. Statistics chosen are meant to represent populations more vulnerable or exposed to extreme heat.

ID	Alias	Population	% DAC	% POC (Percentile)	% Low-Income (Percentile)	% Disabled (Percentile)	% Elderly (Percentile)	% No HS (25+) (Percentile)

HVI (NYC)

The New York City heat vulnerability index is on the neighborhood tabulation (NTA) scale, ranking neighborhoods from 1-5 based on environmental and social factors associated with increased heat risk.

ID	Alias	Air Conditioning (Difference from Avg.)	Median Income (Difference from Avg.)	% Black	HVI (1-5)

HVI (non-NYC)

ID	Alias	Heat Exposure Percentile	Sociodemographic Percentile	Health Outcome Percentile	Heat Vulnerability Index (HVI)

+ Expand Detailed Table

HVI Heat Exposure Indexes

Exposure is measured by the days >85°F heat index and the average maximum heat index (2012-2021) to rank areas by the number of days where negative effects of heat are elevated.

ID	Alias	Days >85°F HI Trend (+)	Avg. Max HI (°F)

HVI Sociodemographic Indexes

The sociodemographic index measures the ability of the population to adapt to instances of high temperature.

ID	Alias	% Black/AA	% Disabled	% Elderly Live Alone	% Low Income	% Limited English	% Outdoor Work

HVI Health Outcome Indexes

ID	Alias	Asthma ED Rate	COPD ED Rate	Heart Attack ED Rate	Diabetes HP Rate	Acute Kidney Failure ED Rate

Key: ED = Emergency Department Visit / HP = Hospitalizations

View how the intensity, duration, and frequency of extreme heat events are affected by a warmer future climate.
Click on the graphs to interact with the maximum heat, length of events, and total number of events across years for selections.

About the Data

Simulations were run with 300-meter land use inputs in the i-Tree Cool Air temperature model. Weather inputs are from the Thermodynamic Global Warming (TGW) climate dataset that reconstructs 2010–2019 weather (Historical 2010s), and applies SSP245 climate-forcing to the same weather patterns in a 40-year projection (Future 2050s). The resulting modeled outputs show how extreme heat could become hotter, last longer, and affect more places. These modeled outputs are not forecasts of how often heat events will occur, and they are not intended to be a 1:1 replication of historical surface observations.

A day qualifies as a heat event when the index is above 95°F for at least two hours. The tool groups heat events into New York State (NYS) & National Advisory and Warning categories. Their definitions are not intended to represent official advisories or warnings issued by National Weather Service (NWS) Weather Forecast Offices, or the criteria those offices use. NYS heat event categories focus on short-duration daytime heat and National classifications highlight multi-day heat with limited nighttime cooling.

Heat event types tracked in the explorer
NYS Heat Advisory: >95F Heat Index for 2+ hours	NYS Heat Warning: >105F Heat Index for 2+ hours	National Heat Advisory: >100F Max Heat Index for 2+ days & min temp >75F	National Heat Warning: >105F Max Heat Index for 2+ days & min temp >75F

Intensity/Duration/Frequency

Compare the decadal differences in heat event characteristics

Intensity:

Highest heat index

Historical (2010s)

Max Heat Index (F)

Future (2050s)

Max Heat Index (F)

Duration:

Average event length

Historical (2010s)

Average Hours

Future (2050s)

Average Hours

Frequency:

Total events

Historical (2010s)

Total # of Events

Future (2050s)

Total # of Events

All Heat Events

Interact with the graphs to view detailed breakdowns of heat events.

Metric

Intensity Duration Frequency

Metric Type

Average Maximum

Average Sum

Time-Averaged Total

View

Historical (2010s)

By Years

ID	Time	Value

By Days

Select a year and month on the graph

Future (2050s)

By Years

ID	Time	Value

By Days

Select a year and month on the graph

View how the temperature type, statistic type, and temperature threshold value change the amount of qualifying days across years and areas.
The graphs summarize the number of days that a given temperature threshold was met or exceeded.

About the Data

The graphs below count days above a temperature threshold using the highest, lowest, or average modeled temperatures within each area. Compare how daily max temperatures behave across air temperature, heat index, and WBGT to identify temperature variations between and within areas.

Temperature

Air Temperature Heat Index (HI) Wet Bulb Globe Temperature (WBGT)

Warmest Hour Statistic

Minimum Mean Maximum

Temperature Threshold

Historical (2010s)

By Year

ID	Time	Days

Future (2050s)

By Year

ID	Time	Days

Click a header to sort values.

Hover over a year column to highlight it. Click a year to switch to monthly view for that year.

Select a Statewide or Local Event to view hourly time series for the historical and future simulated temperatures.
Analyze hourly event intensity, persistence, daytime heating and nighttime cooling between areas and simulated timeframes.

Heat Events

Date

Duration | Max Heat Index (F)

Date

Duration | Max Heat Index (F)

Heat Event Types

Statewide time series are shown for June 29, 2018 through July 5, 2018. This high heat event was simulated at a neighborhood-level (30-meter) scale, containing ten times more detail than the multi-decade, 300-meter simulations used by the Local Events.

Local events are generated when every block group within the selected areas has an overlapping heat event. Each area has stored statistics for the minimum, mean, and maximum temperature for each hour of a heat event, as well as for the two hours before and after the heat threshold is met.

Census block groups are aggregated to the tract level for graph statistics to reduce space and memory requirements. To see block group details, Heat Event Characteristics provides more detailed block group statistics for event duration and maximum heat index.

Event Type	Local Events	State Events
Coverage	Areas with >95F Heat Index	Statewide
Dates Available	Dates where all areas have an event	14 fixed days (historical+future)
Scale	300-meter cellsize	30-meter cellsize
Best For	Comparing multiple heat event severities, understand trends across events; highest coverage for urban areas of similar geography	Block-group comparisons, comparing multiple days in a row; provides temperature comparisons between selected areas with sparse event overlap and/or heat events

Can’t find events for your areas? Ensure you are selecting small census boundaries such as Census Block Groups and Tracts. Hourly data is only generated at the city and county level when all encompassing block groups meet a future heat event.

About the Data

The modeled temperature outputs graphed for Local Events come from 300-meter i-Tree Cool Air simulations using weather based on the Thermodynamic Global Warming (TGW (opens in a new tab)) climate datasets. The Statewide Event uses the same modeling approach at a 30-meter cell size. Historical (2010s) modeled outputs are calibrated representations of long-term historical conditions, not day-for-day reconstructions of observed weather. The Future (2050s) simulation replays the same weather patterns adjusted to an SSP245 warmer climate. After an event is selected, the Historical and Future views allow comparison of the resulting modeled temperatures. The Difference view shows the hour-by-hour future-minus-historical temperature change.

Heat Index	Wet Bulb Globe Temperature (WBGT)
Source Caution (80-90°F) - Fatigue possible with prolonged exposure and/or physical activity Extreme Caution (90-103°F) - Heat stroke, heat cramps, or heat exhaustion possible with prolonged exposure and/or physical activity Danger (103-124°F) - Heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity Extreme Danger (>=125°F) - Heat stroke highly likely	Source

Heat Index

Wet Bulb Globe Temperature (WBGT)

Source

Caution (80-90°F) - Fatigue possible with prolonged exposure and/or physical activity

Extreme Caution (90-103°F) - Heat stroke, heat cramps, or heat exhaustion possible with prolonged exposure and/or physical activity

Danger (103-124°F) - Heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity

Extreme Danger (>=125°F) - Heat stroke highly likely

Source

Event Graph

Select an event from the left to load a graph.

Details

Field	Value
Click on the plot	to populate details