Heat resilience describes how people, households, cities and health systems reduce harm during high temperatures. The measures below span observed deaths, modeled estimates, forecasts, household cooling access, prevention plans and urban interventions, so their definitions and periods should be read carefully.
Key Heat Resilience Statistics
The following figures summarize the most broadly useful heat resilience measures:
- About 489,000 heat-related deaths occurred globally each year in studies covering 2000–2019.
- Asia accounted for 45% of estimated global heat-related deaths during 2000–2019.
- Europe accounted for 36% of estimated global heat-related deaths during 2000–2019.
- Heat-related mortality among people older than 65 increased about 85% between 2000–2004 and 2017–2021 in the global assessment.
- An estimated 61,672 excess heat deaths occurred in Europe in summer 2022.
- Heat claimed 47,500 lives in 35 WHO European Region countries in 2023.
- Annual heat-related deaths in the WHO European Region could reach 120,000 by 2050 without further adaptation.
- The United States recorded 10,527 heat-related deaths during 2004–2018.
- About 90% of U.S. heat-related deaths occurred during May–September in 2004–2018.
- Arizona, California and Texas accounted for 37% of U.S. heat-related deaths during 2004–2018.
- Annual U.S. deaths involving excessive natural heat ranged from 297 to 1,153 between 1999 and 2020.
- El Paso recorded 44 consecutive days above 100°F (37.8°C) during the 2023 Texas/Louisiana heat wave.
- Nearly 90% of U.S. households had air conditioning in 2020.
- Almost 27% of U.S. households maintained an unsafe indoor temperature in 2020.
- Heat prevention plans were associated with a 25.2% reduction in excess deaths across 102 European locations in 14 countries during the 1990–2019 study period.
- Ahmedabad’s heat action plan evaluation estimated 1,190 average annualized deaths avoided after implementation in 2014–2015.
- NWS heat alerts were associated with a −0.5% mortality-rate change across 20 U.S. cities during 2001–2006.
- Tree shading reduced maximum wall and roof surface temperatures by 20–45°F (11–25°C) in a multi-month study of two buildings.
Contents
- Key Heat Resilience Statistics
- Global and Regional Heat Resilience Mortality Statistics
- U.S. Heat Resilience Data on Deaths and Vulnerable Groups
- Heat Exposure Trends and Extreme-Heat Records
- Air Conditioning, Buildings and Household Heat Resilience
- Heat-Health Action Plans and Warning-System Outcomes
- Urban Heat Resilience: Trees, Surfaces and Cooling
Global and Regional Heat Resilience Mortality Statistics
Heat mortality measures are not interchangeable: the global figures below are study-based estimates, while regional figures include excess-mortality estimates and monitored-country totals.
| Measure | Period | Geography | Result |
|---|---|---|---|
| Heat-related deaths | 2000–2019 | Global | About 489,000 per year |
| Share of estimated deaths | 2000–2019 | Asia | 45% |
| Share of estimated deaths | 2000–2019 | Europe | 36% |
| Excess heat deaths | Summer 2022 | Europe | 61,672 estimated |
| Heat deaths | 2022 | 35 WHO European Region countries | More than 60,000 |
| Heat deaths | 2023 | 35 WHO European Region countries | 47,500 |
Source: Heat and health and Heatwaves.
The World Health Organization’s global assessment found that heat-related mortality among people older than 65 increased about 85% between 2000–2004 and 2017–2021. The estimate is a summary of assessed evidence, not a direct count of every heat death.
Europe’s historical benchmarks also show the scale of exceptional events: about 70,000 people died during the June–August 2003 heat event, while the estimated excess-mortality total for summer 2022 was 61,672. These are different event estimates and should not be treated as a like-for-like trend series.
WHO reported that heat-related mortality in the WHO European Region increased 30% over the preceding 20 years. Without further adaptation, annual heat-related deaths in that region could reach 120,000 by 2050, a forecast assuming no further adaptation.
The same WHO regional source reports that the three warmest years on record for the region all occurred since 2020, and that all 10 of its warmest years occurred since 2007. Those rankings depend on the stated observation record and the page’s 2023 update.
U.S. Heat Resilience Data on Deaths and Vulnerable Groups
U.S. mortality series demonstrate why definitions matter. One CDC analysis counted coded heat-related deaths, while another counted deaths involving excessive natural heat as an underlying or contributing cause.
| U.S. measure | Period | Result |
|---|---|---|
| Heat-related deaths | 2004–2018 | 10,527 total; 702 per year on average |
| Deaths in May–September | 2004–2018 | About 90% |
| Male deaths | 2004–2018 | About 70% |
| Arizona, California and Texas | 2004–2018 | 3,852 deaths, or 37% |
| Population represented by those three states | 2004–2018 comparison | About 23% |
Source: Heat-Related Deaths — United States, 2004–2018.
In the 1999–2010 CDC series, 8,081 deaths were reported among the United States and non-U.S. residents in U.S. records. Excessive heat was the underlying cause in 5,783 deaths, or 72%, and a contributing factor in 2,298 deaths, or 28%.
Males represented 5,567 deaths, or 69%, in that series, while adults aged 65 or older represented 2,901 deaths, or 36%. July accounted for 3,145 deaths, or 39%, and August for 2,138, or 26%; urban areas accounted for 81% of heat-related deaths.
Among the 2,298 deaths where hyperthermia was contributory, cardiovascular conditions were the underlying cause in 1,595, or 69%. Across 1999–2020, 15,707 U.S. deaths involved excessive natural heat as an underlying or contributing cause, excluding excessive heat of man-made origin.
Annual deaths in that 1999–2020 series ranged from 297 in 2004 to 1,153 in 2020. Year-to-year reporting and attribution vary, so the range is descriptive rather than a measure of changing risk alone.
Source: QuickStats: Deaths Involving Exposure to Excessive Heat, by Sex — United States, 1999–2020.
Heat Exposure Trends and Extreme-Heat Records
Exposure statistics show how heat can persist across days and extend beyond traditional afternoon peaks.
El Paso recorded 44 consecutive days above 100°F (37.8°C) during the 2023 Texas/Louisiana heat wave. San Antonio exceeded 100°F (37.8°C) on 65 of 78 days from mid-June through the end of August 2023.
Source: A rapid response process for evaluating causes of extreme temperature events in the United States.
In the WHO European Region, heat-stress risk hours for physical activity spread beyond the hottest parts of the day over an approximately 30-year trend. The source presents this as a directional regional indicator rather than a single hour count.
Temperature-related mortality is projected to be 1.91–1.99 times 2010 levels by 2050 in the cited global IPCC assessment. This is a scenario-dependent model result, not an observed mortality total.
Source: Heatwaves and Heat and health.
Air Conditioning, Buildings and Household Heat Resilience
Cooling access is an important resilience capacity, but equipment ownership does not establish affordability, functionality or sufficient indoor protection.
| Household cooling measure | Period | Geography | Result |
|---|---|---|---|
| Households with air conditioning | 2020 | United States | Nearly 90% |
| Central air conditioning | 2015 | United States | 60% |
| Single-unit air conditioners | 2015 | United States | 23% |
| Both central and single-unit systems | 2015 | United States | About 5% |
| Space heating and cooling share of household energy | 2022 | United States | More than 50% |
| Space heating and cooling share of electricity | 2022 | United States | 30% |
Source: U.S. residential cooling and low-income household context.
Low-income U.S. households spent $189 on cooling in 2017, equal to about 2.3% of low-income household energy costs. The cited comparison reported that this low-income cooling burden was more than five times the average home cooling burden of non-low-income households, without supplying the non-low-income dollar denominator in the excerpt.
Almost 27% of U.S. households maintained an unsafe indoor temperature in 2020. The unsafe-temperature definition follows the cited Department of Energy source and is not necessarily limited to heat-only exposure.
Heat-Health Action Plans and Warning-System Outcomes
Intervention evidence often compares observed mortality with a modeled counterfactual or a pre-intervention period. The estimates below therefore indicate associations or modeled outcomes rather than universal randomized treatment effects.
A European study covering 102 locations in 14 countries during 1990–2019 associated heat prevention plans with a 25.2% reduction in excess deaths attributable to extreme heat. Its 95% confidence interval for the reduction was 19.8%–31.9%, with an estimated 1.8 avoided deaths per 100,000 inhabitants annually and 14,551 total deaths avoided after implementation across the study locations.
Source: The effectiveness of heat prevention plans in reducing heat-related mortality across Europe.
| Ahmedabad heat-action measure | Period or threshold | Estimate |
|---|---|---|
| Maximum pre-plan relative risk | 47°C, pre-HAP baseline | 2.34 |
| Maximum post-plan relative risk | 47°C, 2014–2015 | 1.25 |
| Post-to-pre incidence-rate ratio | Above 40°C, 2014–2015 | 0.95 |
| Post-to-pre incidence-rate ratio | Above 45°C, 2014–2015 | 0.73 |
| Avoided deaths | 2014–2015 | 1,190 annualized |
Ahmedabad issued no alert up to 40°C, yellow at 41–42.9°C, orange at 43–44.9°C and red at 45°C or higher. The post-plan relative risks had 95% confidence intervals of 1.02–1.53, while the estimated 1,190 avoided deaths had a 95% confidence interval of 162–2,218.
The Ahmedabad evaluation also reported post-to-pre incidence-rate ratios of 0.95 above 40°C, with a 95% confidence interval of 0.73–1.22, and 0.73 above 45°C, with a 95% confidence interval of 0.29–1.81. The wide interval for the higher threshold illustrates the uncertainty of an ecological pre/post estimate.
Several historical comparisons summarized in the Ahmedabad paper reported lower mortality during later or intervention-associated periods: 4,400 fewer deaths, or 68% below a 2003-based expectation, during Europe’s 11–28 July 2006 period; approximately 29% lower mortality in Shanghai during the 2003 heat wave than in 1998; 23% fewer ischemic-heart-disease deaths among elderly people in a cited Hong Kong study; at least 49% fewer expected deaths in Milwaukee from 1995–1999 after a suite of municipal changes; and roughly 9% lower odds of heat-related mortality among frail elderly people in a cited Florence study. These are secondary results reported within the peer-reviewed Ahmedabad paper, and the warning system alone cannot be isolated for the Milwaukee comparison.
A study of NWS heat alerts across 20 U.S. cities during 2001–2006 found a −0.5% mortality-rate change, with a 95% confidence interval of −2.8% to 1.9%, which includes no association. Philadelphia had a city-specific estimate of a 4.4% lower mortality rate, with a 95% confidence interval of −8.3% to −0.3%.
Source: Effectiveness of National Weather Service heat alerts in preventing mortality in 20 US cities.
Urban Heat Resilience: Trees, Surfaces and Cooling
Urban interventions can reduce the heat absorbed by buildings, but surface measurements should not be read as indoor or ambient-air outcomes.
A multi-month study measured maximum surface-temperature reductions of 20–45°F (11–25°C) on walls and roofs at two buildings under tree shading. The lower end was 20°F (11°C), and the upper end was 45°F (25°C).
Source: Reducing Urban Heat Islands: Compendium of Strategies: Trees and Vegetation.
The result is a building-surface measure, not a direct measurement of air temperature or indoor temperature, and it is site-specific. Together with household cooling access and heat-health planning data, it shows that resilience is multi-layered: exposure reduction, protective buildings, usable cooling and timely public-health action address different parts of the same risk.