(How to Tell If You've Spent Too Much Time Out in the Heat)Warning signs: Lack of sweating

Warning signs: Lack of sweating

When the body reaches a certain internal temperature, its natural defenses—like sweating to release heat—begin to shut down. “If a person’s been outside exercising in the heat and their skin is totally dry, that’s a red flag,” says Dr. Shearer.

However, says Bergeron, it’s not always the case that a person will stop sweating as they enter the danger zone—so don’t assume that just because someone is sweating heavily that they’re okay. (If they have other signs of heat illness, get them help immediately.)