Heat-Related Deaths in the U.S. Have More Than Doubled Since 1999

Jeffrey Howard, an associate professor at the University of Texas at San Antonio, led a team from Pennsylvania State University and the Uniformed Services University of the Health Sciences to analyze two decades of CDC mortality data. By tracking deaths coded for hyperthermia or exposure to excessive natural heat, researchers identified 21,518 total fatalities over the 25-year period. While annual figures fluctuated early on, the data shows a consistent, steady climb in deaths since 2016.

Howard attributes this trend to the increasing frequency and intensity of heatwaves, compounded by social vulnerabilities such as limited access to air conditioning and the plight of unhoused populations. Arizona, California, Nevada, and Texas recorded the highest numbers, reflecting a clear regional risk. The study authors caution that their findings likely underestimate the true death toll due to potential misclassification of causes of death.

The findings have spurred broader legal discussions regarding corporate accountability. A recent memo from the watchdog group Public Citizen suggests that state and local prosecutors could theoretically pursue criminal charges against fossil fuel companies for deaths linked to heat exacerbated by climate change. "These victims deserve justice no less than the victims of street-level homicides," said Aaron Regunberg, senior policy counsel for the organization.