We went through every serious injury employers reported to federal OSHA since 2015 and pulled out the heat cases. There were 2,628, covering 2,631 workers admitted to hospital. Here’s what stood out.
Heat makes up 2% to 3.4% of all severe injuries reported to OSHA. The count peaked in 2016 and 2019, dipped in 2020, and has run between 173 and 248 a year since 2021. It hasn’t fallen.
* 2025 covers January 1 to November 30, the latest data OSHA has published.
OSHA started recording whether heat exposure was indoors or outdoors in 2024. Since then, 53 of 432 heat hospitalizations happened inside: warehouses, plants and kitchens without air conditioning.
That’s the gap indoor rules like Cal/OSHA’s and Minnesota’s are written for. See also cooling for warehouse crews.
California, Washington, Oregon and other state-plan states mostly report elsewhere. Only 127 of 2,628 reports come from them.
These are hospitalizations. Heat illness treated and sent home isn’t here.
Fatalities are reported separately and aren’t in this file.
Employers have 24 hours to report, and heat is often recorded as something else, like a fall or a cardiac event.
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Source. OSHA’s public Severe Injury Reports file, January 1, 2015 to November 30, 2025 (105,996 reports; file dated July 23, 2026; downloaded October 20, 2026).
What counts as heat. Reports OSHA coded as exposure to environmental heat (OIICS 531, or 5310 to 5312 from 2024). Heat burns are excluded. Adding heat-illness diagnosis codes and narrative keywords changes yearly counts by only 0.8% to 5.7%.
Fields. Year from the event date, state from the report, industry from the employer’s primary NAICS code, inspection link from the report’s inspection number.
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