Killer Heat in the United States

The report analyzes future extreme heat in the US, finding that a 'no action' emissions scenario would lead to a staggering increase in dangerously hot days, particularly in the Sunbelt and Midwest, while rapid action could significantly limit these risks.

• Under a 'no action' emissions scenario by midcentury (2036–2065), the average number of days per year with a heat index above 100°F is projected to more than double, and days above 105°F would quadruple compared to the 1971–2000 baseline.
• The number of people exposed to 30 or more days per year with a heat index above 105°F is projected to rise from under 900,000 historically to more than 90 million by midcentury and approximately 180 million by late century under the 'no action' scenario.
• Rapid emissions reductions limiting global warming to 3.6°F (2°C) or less would significantly mitigate these impacts, potentially sparing 114 million people from experiencing a week or more of off-the-charts heat conditions by late century.
• Urban areas are particularly vulnerable due to the urban heat island effect, which can keep city air temperatures up to 22°F warmer than surrounding areas at night.
• The Sunbelt region, including the Southeast and Southern Great Plains, is projected to see the most lifethreatening increases; under 'no action', some areas in southern Florida could experience 170 days per year with a heat index above 100°F.
• In the Midwest and Northern Great Plains, a 'no action' scenario would lead to about 60 million people being exposed to 30 or more days per year with a heat index above 100°F by late century.
• Extreme heat disproportionately threatens vulnerable groups, including outdoor workers (construction and agriculture), the elderly, children, and low-income populations who may lack access to air-conditioning.

APA

Dahl, K., Spanger-Siegfried, E., Licker, R., Caldas, A., Abatzoglou, J., Mailloux, N., Cleetus, R., Udvardy, S., Declet-Barreto, J., & Worth, P. (2019). Killer Heat in the United States. Union of Concerned Scientists. https://www.ucs.org/sites/default/files/2020-12/UCS_extreme_heat_report_190712b_low-res_corrected12-20.pdf

Chicago

Dahl, Kristina, Erika Spanger-Siegfried, Rachel Licker, Astrid Caldas, John Abatzoglou, Nicholas Mailloux, Rachel Cleetus, et al. Killer Heat in the United States. Union of Concerned Scientists, 2019. https://www.ucs.org/sites/default/files/2020-12/UCS_extreme_heat_report_190712b_low-res_corrected12-20.pdf.

Wikipedia

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BibTeX

@techreport{dahl2019killer, author = {Dahl, Kristina and Spanger-Siegfried, Erika and Licker, Rachel and Caldas, Astrid and Abatzoglou, John and Mailloux, Nicholas and Cleetus, Rachel and Udvardy, Shana and Declet-Barreto, Juan and Worth, Pamela}, title = {{Killer Heat in the United States}}, institution = {Union of Concerned Scientists}, year = {2019}, month = jul, url = {https://www.ucs.org/sites/default/files/2020-12/UCS_extreme_heat_report_190712b_low-res_corrected12-20.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }