Global surface temperature has increased by about 2°F relative to 1850–1900. When average temperatures warm, extreme heat becomes more frequent.
According to the latest IPCC reports, the frequency and intensity of extreme heat events has increased around the globe—and these changes are attributed to human-caused climate change.
Extreme heat is the deadliest natural hazard in the U.S. The very young and adults over 65 are among those most vulnerable to heat-related illness and death.
About 85% of the U.S. population lives in metropolitan areas, where urban heat islands can reach peak temperatures up to 20°F hotter than nearby areas with more trees and less pavement.
In major U.S. cities, multi-day heat waves are now lasting longer and occurring three times more often than they did in the 1960s.
With continued heat-trapping emissions, both average temperatures and heat extremes are projected to continue to rise through the 21st century.
In the absence of adaptation measures or reduced exposure of vulnerable people and systems, every bit of additional warming brings greater heat-related risks for health, agriculture, and ecosystems.
These resources explore the science, trends, and local impacts of extreme heat in the U.S.
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