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R48579 — Extreme Heat: Background, NOAA’s Role, and Issues for Congress

Reports · published 2025-06-24 · v1 · Active · crsreports.congress.gov ↗

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Authors
Eva Lipiec
Report id
R48579
Summary

Higher air temperatures, including extreme heat, are associated with adverse impacts on human health, wildlife, and the built and natural environments. Experts estimate that average air temperatures in the contiguous United States have risen since 1970, with the frequency, duration, and intensity of multiday extreme heat episodes across multiple U.S. metropolitan areas also increasing over a similar time period. Average air temperatures and the frequency, severity, duration, and spatial extent of extreme heat episodes are expected to continue to grow into the future. The term extreme heat is often used interchangeably with related terms, such as excessive heat, heat index, wet bulb globe temperature, and heatwave, among others. There is no one definition for extreme heat, and entities may use different atmospheric, geographic, and social factors to define extreme heat. The factors that comprise risk from extreme heat include the frequency, duration, and intensity of extreme heat episode (i.e., the hazard) and the exposure and vulnerability of communities to the episodes. The National Oceanic and Atmospheric Administration (NOAA), within the Department of Commerce, has led or supported extreme heat-related observations, forecasting, modeling, communication, research, and coordination. NOAA has applied its authorities primarily to work on extreme heat as a hazard; however, some of NOAA’s activities also address aspects of extreme heat exposure and vulnerability. Other federal agencies have a greater role than NOAA in these other components of extreme heat risk. NOAA’s extreme heat-related activities occur across its sub-agencies or line offices, including the National Environmental Satellites, Data, and Information Service (NESDIS), National Ocean Service (NOS), National Weather Service (NWS), Office of Oceanic and Atmospheric Research (OAR), and Office of Marine and Aviation Operations (OMAO). NOAA has coordinated with other agencies on extreme heat-related activities through mechanisms such as the National Integrated Heat Health Information System (NIHHIS); NOAA and the Centers for Disease Control and Prevention, with representatives from several federal departments and agencies, established NIHHIS with the goal “to develop and provide actionable, science-based information to help protect people from heat.” Members of Congress may continue to consider evaluating NOAA’s existing activities, potential additional actions the agency could take to address extreme heat, funding for said activities, and the agency’s role in coordinating with other federal agencies and nonfederal entities working to address the various aspects of extreme heat. Some stakeholders have argued for NOAA to implement or support certain activities—observations, modeling, forecasts, communications, research, and coordination—related to understanding and addressing extreme heat as a hazard. Likewise, some have advocated to expand the agency’s role in understanding and addressing extreme heat exposure and vulnerability. Others, including the Trump Administration, have proposed or made changes to NOAA staffing and funding, the impacts of which for the agency’s existing and future extreme heat-related activities remain unclear.

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