Rise in Heat Related Mortality in the United States

Over the past century, extreme heat events (EHE) 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 EHEs can vary significantly between events and over time, with some events perceived as more severe producing vastly different health and societal outcomes and these factors are 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 connected to increases in annual EHE days during the period, suggest a significant escalation in heat related risk in the United States. Further, we find 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.