Heat claims the lives of thousands of Americans annually, yet this cause is often underreported. As climate change amplifies summer heat, the true extent of heat-related deaths in the U.S. remains unaccounted for. The current system for data collection is inconsistent, leading to significant undercounting. Addressing this gap is key to preventing more fatalities.

NPR teamed up with Boston University to produce a comprehensive estimate of heat-related deaths nationwide. This investigation spanned two years and involved constructing a statistical model covering nearly every county. The full findings are slated for publication in a scientific journal.

Quinn Adams from Boston University emphasizes the importance of an accurate assessment. Understanding who is affected, where, and why is crucial for creating effective solutions. Apart from statistics, NPR seeks to highlight personal stories of those who might not have perished if not for the extreme heat. These narratives will be shared in upcoming reports.

Underreporting Heat-Related Deaths

The U.S. sees a substantial undercount of heat-related fatalities. The Centers for Disease Control and Prevention (CDC) is the primary record keeper. From 2004 to 2018, their records showed an average of around 700 deaths yearly due to heat. Recently, this number increased to about 1,700 annually. However, the collaborative analysis from NPR and BU suggests the real average is closer to 9,000 deaths each year from 2018 to 2025. In some years, the figure surpasses 10,000.

“The data is clear: Heat can take anyone, anywhere in the country.” – Quinn Adams

Climate change intensifies these dangers. Heatwave seasons have lengthened since the 1960s. In major cities, the number of heat waves has doubled since the 1980s. Heat domes expose millions to dangerous heat levels.

Why Underreporting Occurs

Doctor Sameed Khatana explains that heat’s role in death is subtle. Conditions like heart attacks overshadow it. Heat can exacerbate existing illnesses, making them fatal. Often, heat is not marked on death certificates, leading to omissions in official records. This oversight creates a nationwide blind spot.

Heat’s Reach Across the Nation

Heat-related deaths occur all over the U.S. Data shows states like Florida and Texas have high numbers due to large populations. Even less traditionally hot states report significant fatalities. In Michigan, over 100 people die annually from heat, far exceeding official reports.

Infrastructure plays a role. States unaccustomed to heat lack proper cooling measures. For instance, in Washington state, only 53% of homes have some form of air conditioning.

Progress in Reporting, Yet Challenges Persist

Official counts are improving due to better recording methods. However, some areas still lag behind. Maricopa County in Arizona stands out with effective strategies to detect heat-related deaths, including investigating air conditioning availability and medication use.

In Los Angeles, the true impact is higher than reported, but refining data collection proves challenging. Efficient protocols require time and training, which many hospitals and counties currently lack.

Unless addressed, undercounting will obscure the reality of heat’s dangers. Adams underscores the urgency, stating many people underestimate their vulnerability to heat.

NPR will continue its exploration, documenting overlooked deaths and investigating paths to prevention.

This research received support from the Nova Institute for Health Media Fellowship and the Dennis A. Hunt Fund for Health Journalism. Nick McMillan contributed to this report.