As heat records fall, how hot is too hot for the human body?

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W. Larry Kenney, Penn State; Daniel Vecellio, Penn State; Rachel Cottle, Penn State, and S. Tony Wolf, Penn State

(THE CONVERSATION) Extreme heat has been breaking records across Europe, Asia and North America, with millions of people sweltering in heat and humidity well above “normal” for days on end.

Death Valley hit 128 degrees Fahrenheit (53.3 degrees Celsius) on July 16, 2023 – not quite the world’s hottest day on record, but close. Phoenix broke a record heat streak with 19 straight days with temperatures above 110 F (43.3 C), accompanied by a long string of nights that never got below 90 F (32.2 C), leaving little...