Rise in heat related mortality in the United States

Over the past century, extreme heat events (EHEs) have become more frequent and intense, resulting in significant health impacts and economic challenges worldwide. In the United States, extreme heat is the leading weather-related cause of death, claiming more lives annually than hurricanes, floods, and tornadoes combined. However, the characteristics of extreme heat events can vary widely across events and over time. Even events perceived as similarly severe can result in vastly different health and societal outcomes—differences that remain largely understudied. In this paper, we explore regional trends in heat severity and mortality rates across the conterminous United States from 1981-2022 and provide a regional examination of how specific EHE characteristics impact heat mortality. We find that the number of extreme heat days has the strongest influence on heat related mortality. We observe increasing trends in heat-related mortality in every climate region throughout the U.S., except for the Western North Central region. These increases—likely tied to rising counts of annual EHE days—signal a structural shift to a new, elevated baseline of heat-related mortality in the U.S. Further, in the Southwest and Southeast regions, heat-related mortality is increasing at a higher rate than heat severity, suggesting potential for modification by community and individual level social vulnerability. Future heat mortality models should be holistic in their approach, incorporating not only multiple characteristics of heat but also measures of vulnerability to fully capture the complex dynamics of risk and exposure.