Extreme Heat

Across the country, climate change is making heat waves hotter and more frequent.^a If that isn't reason enough to sweat, consider the health impacts: As temperatures rise, so do the number of heat-related illnesses, emergency room visits, and deaths. Heat waves have been the top cause of U.S. weather fatalities, on average, over the past 30 years.^b

Explore the map by clicking on a state or clicking on the magnifying glass to type in your address. Areas with more than 9 days of extreme heat are living with more days of extreme heat than they did in the past, based on historical records.

Find out how we did the map and analysis >>

Our analysis shows that nearly 210 million Americans—or two-thirds of the population—live in counties vulnerable to health threats from unexpectedly high summer temperatures,^c which can cause heat exhaustion and heatstroke or worsen preexisting cardiovascular and respiratory conditions.^d An estimated 1,300 excess deaths occurred annually during extreme summer heat from 1975 to 2004,^e and more than 65,000 people end up in emergency rooms each summer with heat-related illnesses.^f

Older adults, young children, people with chronic illness, lower-income communities, some communities of color, and people who work or exercise outdoors are among the populations most vulnerable to heat-related health effects.^g City residents also face a heightened risk because of warmer temperatures in cities from the urban heat island effect, caused by the mostly paved surfaces that absorb and re-radiate heat and the lack of green spaces and tree cover in these areas.^h

Through August, 2017 has been the third-hottest year on record in the continental United States, with Florida, Georgia, North Carolina, and South Carolina all registering new highs for the first eight months of a year.ⁱ The United States has warmed by about 1.5°F since 1895, with most of the rise occurring since 1970.^j If the world continues to increase emissions of carbon pollution, the country could see 5°F to 10°F of additional warming by the end of the century.^k

Increases in extreme heat could cause a dramatic rise in illnesses and deaths by the end of the century. For instance, large urban areas such as New York, Philadelphia, Chicago, and Boston could each experience at least six times as many dangerously hot summer days by 2100 as they did, on average, from 1975 to 2010.^l Collectively, 45 major urban areas in the United States could see about 28,000 more deaths each year due to extremely hot summer days by the 2090s.^m

But we aren’t doomed to this fate. We can keep future climate warming in check and avoid the health threats of climate change by:

• Calling on companies and decisionmakers at all levels of government to help reduce climate-wrecking carbon pollution from power plants, vehicles, and other sources.
• Ensuring our state and local governments are prepared for the health threats of climate change. Today, fewer than one-third of U.S. states have developed a plan to address the health impacts of a warming planet.ⁿ
• Taking steps to protect ourselves on dangerously hot days.^o

Citations

a. U.S. Global Change Research Program, The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment, chapter 2, “Temperature-Related Death and Illness,” 2016, https://health2016.globalchange.gov/temperature-related-death-and-illness.
b. National Weather Service, Natural Hazard Statistics, “Weather Fatalities 2016,” http://www.nws.noaa.gov/om/hazstats.shtml, 2017.
c. For more information on our analysis, please see Frequently Asked Questions. NRDC analysis of data from NOAA, Global Historical Climatology Network (GHCN), https://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/global-historical-climatology-network-ghcn (accessed June 15, 2017); and U.S. Census Bureau, “2011–2015 American Community Survey 5-Year Estimates,” 2015, https://factfinder.census.gov (accessed June 15, 2017).
d. U.S. Global Change Research Program, The Impacts of Climate Change on Human Health.
e. Kalkstein, L.S., et al., “An Evaluation of the Progress in Reducing Heat-Related Human Mortality in Major U.S. Cities,” Natural Hazards 56, no. 1 (2010): 113-129, https://link.springer.com/article/10.1007%2Fs11069-010-9552-3 (accessed July 21, 2017).
f. Hess, J. J., et al., “Summertime Acute Heat Illness in U.S. Emergency Departments from 2006 Through 2010: Analysis of a Nationally Representative Sample,” Environmental Health Perspectives 122, no. 11 (2014): 1209-1215, https://ehp.niehs.nih.gov/1306796/, (accessed July 21, 2017).
g. U.S. Global Change Research Program, The Impacts of Climate Change on Human Health.
h. U.S. Environmental Protection Agency, “Reducing Urban Heat Islands: Compendium of Strategies—Draft,” 2008, www.epa.gov/heat-islands/heat-island-compendium, (accessed July 21, 2017).
i. NOAA, National Centers for Environmental Information, “Assessing the U.S. Climate in August 2017,” 2017, https://www.ncei.noaa.gov/news/national-climate-201708, (accessed September 8, 2017).
j. U.S. Global Change Research Program, Climate Change Impacts in the United States: The Third National Climate Assessment, chapter 2, “Recent U.S. Temperature Trends,” 2014, http://nca2014.globalchange.gov/report/our-changing-climate/recent-us-temperature-trends (accessed July 21, 2017).
k. Ibid.
l. Natural Resources Defense Council, “Killer Summer Heat: Paris Agreement Compliance Could Avert Hundreds of Thousands of Needless Deaths in America’s Cities,” 2017, https://www.nrdc.org/sites/default/files/killer-summer-heat-paris-agreement-compliance-ib.pdf (accessed June 29, 2017).
m. Ibid.
n. 1. Georgetown Climate Center, “State and Local Adaptation Plans,” 2017, http://www.georgetownclimate.org/adaptation/index.html (accessed June 29, 2017).
o. For more information on how we can protect ourselves from extreme heat, see Frequently Asked Questions.