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About the data sources on this website.

Cite the data

New York City Department of Health, Environment & Health Data Portal. Climate data: . Accessed at https://a816-dohbesp.nyc.gov/IndicatorPublic/data-explorer/climate/ on Oct 16, 2026. Copy citation.

Heat vulnerability index (NTA)

The risk of community-level heat impacts, like deaths, due to extreme heat events. The HVI is made up of data on surface temperature, green space, air conditioning access, median income, and Black population (the population most excluded from heat resources). Differences in community-level heat impacts stem from structural racism, which limits access to preventive resources.

Heat vulnerability index

The risk of community-level heat impacts like deaths due to extreme heat events. The HVI is made from data on surface temperature, green space, air conditioning access, median income, and Black population (the population most excluded from heat resources). Differences in community-level heat impacts stem from structural racism, which limits access to preventive resources.

Heat events

Days over 90 degrees. More people die due to extreme heat than all other extreme weather events combined. As the climate continues to warm, we can expect more severe and more frequent heat events.

Daytime summer surface temperature

Spatial average of surface temperature, measured by satellite. Surface temperatures vary because of vegetative cover (which promotes cooling), and paved roads, sidewalks, and buildings (which retain heat). Hotter neighborhoods tend to have more heat-exacerbated deaths associated with extreme heat events.

Vegetative cover

Land covered by trees, grass, or other plants. Vegetative cover reduces temperatures in the immediate area, and may increase air quality.

Adults with air conditioners

Adults reporting having an air conditioner. Air conditioning reduces the risk of heat stroke and other heat-related illness.

Household air conditioning

Households reporting functioning air conditioning (AC). AC is an important way to prevent heat stress, especially for people with limited mobility.

Households using electric medical equipment

Households with someone using electric medical equipment. People who use electric medical equipment are more vulnerable during power outages or evacuations.

Residents living in a hurricane evacuation zone

Hurricane Evacuation Zones are determined by New York City Emergency Management and indicate varying threat levels of coastal flooding from storm surge. Evacuation orders may be given during hurricanes or coastal flooding events. There are six zones, ranked by storm surge risk. Zone 1 is the highest risk for flooding. Residents in these zones may receive evacuation orders during hurricanes or tropical storms.

Climate

A region’s climate is characterized by its usual weather conditions, seasons, and patterns in extreme weather events like heat waves, droughts, and hurricanes.

The world’s climate is shifting, becoming warmer with more precipitation and weather extremes. Over the past century in New York City, average temperatures have increased by 0.25°F per decade, precipitation by 0.72 inches per decade, and sea levels by 1.2 inches per decade. By the 2020s, a projected 25-30 days above 90°F are expected in a typical summer, resulting in more frequent and intense heat waves. Rainfall and precipitation are expected to increase by up to 5%, together with another 10 inches of sea level rise and increased probability of coastal storms with flooding (NYC Panel on Climate Change, Climate Risk Information, 2009).

Climate and Health

Even without long term changes in climate, New Yorkers face weather-related risks today. Heat and humidity cause serious illness and death every summer. In fact, more Americans die from heat waves in a typical year than all other natural disasters combined, both in direct mortality from heat stress (hyperthermia, also known as heat stroke) and by way of increases in the usual rates of deaths from natural causes due to the exacerbation of other medical conditions.

While less common, coastal storms also have imparted serious consequences throughout history and in recent years, most notably Hurricanes Katrina and Rita in 2005, from their devastating direct costs in over 1,800 lives along the Gulf Coast, to long-term mental health consequences among survivors. In 2011, Tropical Storm Irene caused extensive flooding throughout the Northeast and is estimated to be one of the costliest disasters in U.S. history, though New York City was largely spared.

The health impacts of weather events and climate change may be further compounded by power outages arising during heat waves and coastal storms. Such effects include gastrointestinal illness due to food spoilage, acute carbon monoxide poisoning from the use of generators, and illness and death among the medically frail due to mechanical equipment failure, lack of air conditioning, inability to obtain medical care, or extreme exertion (such as having to climb many flights of stairs due to elevator outages).

About the Data and Indicators

The Tracking Portal provides data on counts and rates of death, hospital admission, and treatment in an emergency department for heat stress. While these cases can be readily identified with hyperthermia listed as a diagnosis or cause of death, it is important to note that they reflect only a portion of the overall health impact of extreme heat. Increases in natural-cause hospitalization and death rates during heat waves (from cardiovascular disease, diabetes, and renal disease for example) may be estimated using statistical methods.

Prevention

Air conditioning is the most important way to prevent heat stress and death on hot days.

Being prepared is key to weathering hurricanes and coastal storms safely.

Key Messages

About 80% of heat stroke victims in New York City are overcome by excessively hot conditions in their own homes, as indoor temperatures in the urban environment may be even hotter than outdoor temperatures when an air conditioner is not available or not in use.

While heat-related mortality rates are overall substantially lower than in historical periods before electricity and air conditioning (a notorious heat wave in 1896 killed approximately 1,500 NYC residents), we may begin to see a reversal in this trend as a result of rising temperatures, depending on the extent of adaptation. In 2011, a Health Department survey estimated that 25% of New York City adults still do not have or rarely use air conditioning during hot summer weather, many of whom are at increased risk of heat stress due to age or poor health.

Concerned about this? Email your elected officials.