How Hot is Too Hot?

“What is the hottest ‘room’ temperature at which a human body can, by sweating, keep itself cool enough to avoid health damage?”

— Matt B., Etterzhausen, Germany

It’s not the heat, it’s the humidity.

Your body avoids overheating by taking advantage of a bit of physics: When water evaporates from a surface, it leaves the surface cooler. When your body gets too hot, it pumps water onto your skin and lets it evaporate, carrying away heat. This effect can actually lower the temperature of your skin to below the air temperature. This allows humans to survive in places where the air temperature is as high as human body temperature — as long as we keep drinking water to produce more sweat.