America has no official count of climate-related deaths. An Arizona examiner is trying to fix that.

Greg Hess, the medical examiner for Pima County, Arizona, has developed strategies to count heat-related deaths in a region where extreme temperatures are a recurring danger. His work also points to a wider gap in the United States: no government agency, research institution or state authority maintains official records of climate-fuelled deaths across the country.

Pima County lies along the United States-Mexico border, and its medical examiner's office handles some 3,000 deaths each year. From April through October, Hess's morgue drawers fill with people who died from Arizona's heat.

Hess and his team have developed some of the most innovative methods for counting people who die from heat-related problems. The brief does not specify the procedures they use or their results. Even so, the effort illustrates the importance of detailed local investigation where heat can contribute to a death.

A small group of health experts around the country has concluded that thousands of Americans die each year because of climate-fuelled disasters. There is no official national system that brings such deaths into a single record.

That absence makes it difficult, and at times impossible, to measure the full effect of weather disasters on families and communities. Incomplete records also limit public health planning intended to prevent future deaths, including decisions about when and where to locate cooling centres during a heat wave.

Kristie Ebi is a public health and climate epidemiologist at the University of Washington. The need for reliable mortality data is particularly pressing in Arizona, where heat kills more people than any other weather event year after year.

Arizona records more days over 110 degrees than any other state. 2023 was one of the hottest years ever recorded in Arizona. Both 2023 and 2024 also broke records for the most nights when temperatures never dropped below 90 degrees.

Heat-related deaths are almost always preventable. According to the National Weather Service, the 10 year-average of heat fatalities in the U.S. is twice as high as any other weather hazard.

Local efforts such as Hess's can improve the accounting of deaths in a particular county. They do not provide a national picture. Without consistent official tracking across jurisdictions, public health authorities lack a complete basis for judging where preventive measures are most needed during periods of dangerous heat.