“Temperatures also don’t have to be very high for strenuous work to become deadly. The lack of heat acclimatization all too frequently kills workers; the majority of workers who die from heat do so in the first few days at work. “A lot of workers will actually end up in heatstroke during the first week on the job,” says Brenda Jacklitsch, a health scientist at the National Institute for Occupational Safety and Health (NIOSH).
Extreme heat is also affecting productivity. According to a 2022 study by The Lancet, which is tracking the relationship between climate change and public health, about 470 billion hours of labor were lost in 2021 due to extreme heat. The US alone lost 2.5 billion hours, mostly in the construction, manufacturing, service, and agriculture sectors.”
https://www.vox.com/23844420/extreme-heat-work-labor-osha-climate-change