Extreme heat is measured through temperature records, heatwave exposure, illness, deaths, lost work, cooling access, and energy use. The statistics below span global and regional observations, estimates, surveys, and forecasts, with measurement periods and population definitions kept explicit.
Key Extreme Heat Statistics
The most broadly useful extreme heat statistics include:
- In 2024, the global mean surface temperature was 1.55°C above the 1850–1900 average worldwide, with a ±0.13°C uncertainty margin.
- From 2015 through 2024, every year ranked among the ten warmest years on record globally.
- From 2000–2019, about 489,000 heat-related deaths occurred each year on average worldwide, based on studies summarized by WHO.
- Between 2000–2004 and 2017–2021, heat-related mortality among people aged 65 and older increased about 85% globally.
- During summer 2022, an estimated 61,672 heat-related excess deaths occurred in Europe.
- In 2023, CDC recorded 119,605 heat-related illness emergency-department visits in the United States through NSSP/ESSENCE.
- In the United States during May–September 2023, the overall heat-related illness emergency-department rate was 180 per 100,000 ED visits.
- In 2023, U.S. heat exposure caused an estimated 3.4 billion potential labor hours to be lost.
- In 2023, potential U.S. income loss from reduced labor due to heat reached US$103 billion.
- In 2023, global heat exposure caused an estimated 512 billion potential work hours to be lost.
- In a 2030 ILO forecast, heat stress could cost 2.2% of total working hours worldwide under a 1.5°C scenario.
- In the same 2030 forecast, heat-stress productivity losses were equivalent to 80 million full-time jobs worldwide.
- About 1.2 billion people globally are at high risk of health, productivity, and nutrition problems because they lack adequate cooling.
- Cooling used about 20% of global electricity in the 2022 baseline.
- In 2020, 88% of U.S. households used air conditioning, according to the EIA RECS survey.
- In 2020, air conditioning accounted for 19% of U.S. residential electricity consumption.
Contents
- Global temperature and heatwave trends
- Population exposure and vulnerability
- Heat-related mortality and health outcomes
- U.S. heat illness and regional burden
- Work capacity and economic costs
- Cooling access, adoption, energy, and mitigation
Global Temperature and Heatwave Trends
The World Meteorological Organization’s six-dataset consolidation identifies 2024 as the warmest year on record. Its global mean surface temperature was 1.55°C above the 1850–1900 average, with a ±0.13°C uncertainty margin; this is an observed global anomaly, not a forecast. WMO: “WMO confirms 2024 as warmest year on record at about 1.55°C above pre-industrial level”
The recent record is part of a sustained sequence: every year from 2015 through 2024 ranked among the ten warmest years on record globally. The same WMO source reports that upper-2,000-meter global ocean heat content rose by 16 zettajoules from 2023 to 2024, while an estimated 90% of excess heat from global warming is stored in the ocean. WMO: “WMO confirms 2024 as warmest year on record at about 1.55°C above pre-industrial level”
| Global measure | Period | Result | Geography or definition |
|---|---|---|---|
| Mean surface temperature anomaly | 2024 | 1.55°C | Above 1850–1900 average, global |
| Warmest-year ranking | 2015–2024 | 10 years | Every year in the top ten, global |
| Upper-2,000-meter ocean heat content change | 2023–2024 | 16 zettajoules | Global ocean |
| Excess heat stored in ocean | Long-term assessment | About 90% | Global warming excess heat |
The WMO temperature figure is observed but carries the stated uncertainty; the ocean-storage figure is an estimate. These measures describe different parts of the climate system and should not be treated as interchangeable heatwave-day counts.
Population Exposure and Vulnerability
WHO’s summary of studies covering 2000–2019 estimates an average of about 489,000 heat-related deaths per year globally. The source notes that the studies vary in attribution and coverage, so this is an estimate rather than a single global death registry total. WHO: “Heat and health”
The regional distribution in those studies was uneven. Asia accounted for 45% and Europe for 36% of estimated global heat-related deaths during 2000–2019, while heat-related mortality among people aged 65 and older increased about 85% between 2000–2004 and 2017–2021 globally. WHO: “Heat and health”
| Population or region | Period | Heat-related measure |
|---|---|---|
| Global population | 2000–2019 | About 489,000 deaths per year on average |
| Asia | 2000–2019 | 45% of estimated global deaths |
| Europe | 2000–2019 | 36% of estimated global deaths |
| People aged 65+ worldwide | 2000–2004 to 2017–2021 | About 85% increase in mortality |
More than 2.4 billion workers were exposed to excessive heat in the 2024 report assessment by the International Labour Organization. The worker-exposure figure and the mortality estimates measure different populations and outcomes, so neither is a direct conversion of the other. ILO: “Increase in heat stress predicted to bring productivity loss equivalent to 80 million jobs”
Heat-Related Mortality and Health Outcomes
Several European episodes show the scale of acute heat mortality estimates. WHO reports 61,672 heat-related excess deaths in Europe during summer 2022, about 70,000 deaths during the June–August 2003 European heatwave, and about 56,000 excess deaths during a 44-day heatwave in the Russian Federation in 2010.
These are episode-specific estimates with different geographies and periods. WHO: “Heat and health”
The WHO European Region’s heat-related mortality increased 30% over an approximately 20-year comparison. Under a no-further-adaptation scenario, annual heat-related deaths in that region could reach 120,000 by 2050; this is a forecast, not an observed count. WHO Europe: “Heatwaves”
In the United States, infants experienced an average of 9.3 heatwave days per year during 2014–2023, compared with 8.4 days per year for adults aged 65 and older. These are population-specific exposure estimates, not mortality rates. 2024 Lancet Countdown U.S. Brief
U.S. Heat Illness and Regional Burden
CDC recorded 119,605 heat-related illness emergency-department visits in NSSP/ESSENCE during January–December 2023. Ninety-two percent occurred during May–September, and the overall mean rate during that warm season was 180 HRI ED visits per 100,000 ED visits, compared with 151 during May–September 2018–2022 among facilities with consistent reporting and data-quality filters. CDC: “Heat-Related Emergency Department Visits—United States, May–September 2023”
The CDC rates are ED-visit rates from participating NSSP/ESSENCE facilities, not population incidence. The average rate was 303 per 100,000 ED visits in July–August, versus 97 in May, June, and September, and the 2023 rate was 271 for males versus 104 for females. CDC: “Heat-Related Emergency Department Visits—United States, May–September 2023”
| U.S. group or period | 2023 HRI ED rate |
|---|---|
| July–August average | 303 per 100,000 ED visits |
| May, June, and September average | 97 per 100,000 ED visits |
| Males | 271 per 100,000 ED visits |
| Females | 104 per 100,000 ED visits |
| Overall May–September | 180 per 100,000 ED visits |
Age-specific rates during May–September 2023 were 211 per 100,000 ED visits for ages 18–25, 222 for ages 26–54, 207 for ages 55–64, 173 for ages 65–74, and 120 for ages 75 and older. The 18–25 rate was 2.52 times the rate for people younger than 18 in a multivariate Poisson regression using that group as the referent. CDC: “Heat-Related Emergency Department Visits—United States, May–September 2023”
Regional persistence also varied. HRI ED rates exceeded the 2018–2022 95th-percentile baseline for 16 consecutive days in HHS Region 6 and 18 consecutive days in HHS Region 9 during July 2023; in Region 6, 37% of May–September warm-season days exceeded that threshold. CDC: “Heat-Related Emergency Department Visits—United States, May–September 2023”
Work Capacity and Economic Costs
The ILO estimates that global heat exposure caused 512 billion potential work hours to be lost in 2023, 49% above the 1990–1999 average. For the United States, the corresponding estimate was 3.4 billion potential labor hours, 69% above its 1990–1999 annual average. ILO: “Increase in heat stress predicted to bring productivity loss equivalent to 80 million jobs”
The U.S. heat-related labor estimate corresponded to US$103 billion in potential income loss in 2023. These are modeled potential losses from reduced labor capacity, not reported payroll deductions or a count of people permanently leaving work. 2024 Lancet Countdown U.S. Brief
| Measure | Period | Estimate or forecast |
|---|---|---|
| Global potential work hours lost | 2023 | 512 billion; 49% above 1990–1999 average |
| U.S. potential labor hours lost | 2023 | 3.4 billion; 69% above 1990–1999 average |
| U.S. potential income loss | 2023 | US$103 billion |
| Global working hours lost | 2030 forecast | 2.2% under a 1.5°C scenario |
| Global full-time-job equivalent | 2030 forecast | 80 million |
| Global economic loss | 2030 forecast | US$2.4 trillion |
Under the ILO’s 2030 forecast, 2.2% of total working hours worldwide could be lost to heat stress under a 1.5°C scenario, equivalent to 80 million full-time jobs and US$2.4 trillion in global economic loss. The forecast assumes shaded agriculture and construction work; the job figure is a productivity-loss equivalent, not literal job separations.
Agriculture is projected to account for 60% of lost global working hours. ILO: “Increase in heat stress predicted to bring productivity loss equivalent to 80 million jobs”
Cooling Access, Adoption, Energy, and Mitigation
UNEP estimates that about 1.2 billion people are at high risk of health, productivity, and nutrition problems because they lack adequate cooling. At the same time, cooling used about 20% of global electricity in the 2022 baseline. UNEP: “Cooling” UNEP: “Global Cooling Watch 2023 Keeping it Chill”
Under current policies, global installed cooling-equipment capacity is projected to reach three times the 2022 baseline by 2050, while cooling-related emissions could reach 6.1 billion metric tons of CO2e. UNEP also estimates that sustainable-cooling measures could cut more than 60% of projected 2050 cooling emissions in a scenario requiring passive cooling, efficiency standards, and HFC phase-down. UNEP: “About Cooling” UNEP: “Global Cooling Watch 2023 Keeping it Chill”
In the United States, the EIA’s 2020 RECS survey found that 88% of households used air conditioning. Usage was 93% in the South, 92% in the Midwest, and 73% in the West; the survey covered 18,496 responding households. EIA: “Nearly 90% of U.S. households used air conditioning in 2020”
| U.S. household measure | Period | Share |
|---|---|---|
| All households using AC | 2020 | 88% |
| South households using AC | 2020 | 93% |
| Midwest households using AC | 2020 | 92% |
| West households using AC | 2020 | 73% |
| Homes built before 1950 using AC | 2020 | 83% |
| Homes built 2010–2020 using AC | 2020 | 93% |
The EIA also reports that AC use rose from 57% of U.S. homes in 1980 to about 89% in 2020, while central AC rose from 27% to 67% over the same period. AC accounted for 19% of U.S. residential electricity consumption in 2020; annual end-use shares vary with weather. EIA: “Electricity use in homes”