If our body heat is 98.6...

The human body is a little heat-producing engine, generating its own internal warmth. When the outside air is cold, our bodies do a pretty good job of producing heat to warm us up. But when the outside temperature gets to be as hot as 98.6 degrees F, we just keep producing heat. That’s when we start to sweat, as a means of regulating our internal temperature. At very high temperatures, we have trouble giving off enough sweat to cool ourselves down.