How Hot is Too Hot for Humans?

August 28, 2022

How our bodies use a “Physics hack” to keep us cool.
It has limits.

Good explainer of a slippery concept.


There’s a temperature threshold beyond which the human body simply can’t survive — one that some parts of the world are increasingly starting to cross.

Key Details

  • “Wet bulb temperature” is a measure of heat and humidity, essentially the temperature we experience after sweat cools us off.
  • In Death Valley, California, one of the hottest places on Earth, temperatures often get up to 120 degrees F — but the air is so dry that it actually only registers a wet body temperature of 77 degrees F.
  • When the wet bulb temperature gets above a certain point, our bodies lose their ability to cool down, and the consequences can be deadly.

Jeff Masters and I discussed a few months ago, below.

2 Responses to “How Hot is Too Hot for Humans?”

  1. It’s a terrific question. 🙏

  2. Anthony O'Brien Says:

    A wet bulb temp of 95F is a sit in the shaded and do nothing limit. Your ability to do actual work is affected much earlier. Try doing laps in a pool heated to 82 F, it is too hot for laps. 82 F is OK for play and relaxing, not for laps.

    Long before a wet bulb of 82F, managing the bodies salt levels becomes a complex time sensitive task. Yes you can get to know the signs, but by then it is already getting dangerous.

    You are talking about a world where you have to be very careful how you go to do number two’s.

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