Extreme Heat Is Taking A Bigger Toll Than We Thought

Health

There's a pretty clear correlation between how hot it is and how many people are hospitalized as a result. Here's what new findings revealed.

BySean Breslin•August 2, 2025

A woman holds a purple umbrella to shield herself from the sun while standing in front of the Parthenon — A tourist holds an umbrella to shield herself from the sun as she and others walk in front of the 5th century B.C. Parthenon temple on the Acropolis hill during a heat wave in Athens, Friday, July 25, 2025.
(AP Photo/Petros Giannakouris)

It's bad enough that hotter summers are making us sicker, but according to a new study, it's even worse than we thought.

Published Wednesday in the journal Science Advances, the findings revealed that emergency room visits increase — especially with young children — as temperatures rise. The study used 11 years of data from 2006 to 2017 in California emergency rooms and found that hospitals are increasingly burdened with sick individuals the hotter it gets.

So, although it was already known that both extreme heat and brutal cold contribute to a rise in deaths, it's the heat that's making us even sicker, and that means more stress on vital organs.

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(MORE: This Is The Hidden Danger Of Heat Waves)

The dangerous trend is getting worse as the planet continues to warm, setting more extreme heat records each year and expanding the zones where extreme heat is found.

"It is helpful to have more detailed analyses of temperature-morbidity relationships, to help identify interventions that could decrease hospitalizations during heat waves," Kristie Ebi, a professor at the Center for Health and Global Environment at the University of Washington, told the Washington Post.

Some experts caution that the findings might be different outside of California, especially because not every state (and country outside the United States) is as exposed to smoke as Californians were from 2006 to 2017, but the study's authors said they're confident that the tie between hotter temperatures and more hospitalizations is a widespread issue.

"Even when heat doesn’t kill, it hurts a lot," lead author Carlos Gould, who works as an environmental health scientist at the University of California San Diego, told the Washington Post.

More findings from the study:

- Increased temperatures led to a jump in the number of people hospitalized for illnesses like respiratory and nervous system problems.

- This was especially true for children under 5, more than any other age group.

And to learn more about what extreme heat does to the body, click here.