If the temperature outside is greater than 90 degrees or if the sun is shining, your body will also be heated by the environment, Dr. Kavouras said. “As you’re adding this huge external heat source, the body’s got to deal with that,” said Glen Kenny, a physiologist who studies the body’s stress response at the University of Ottawa. The main way the body sheds heat is through the evaporation of sweat, which cools the surface of the skin, Dr. Kavouras explained. This happens more easily in dry heat than in humidity, but in dry heat, sweat can evaporate so quickly that you may not notice it. “You don’t even see it and you don’t even know that you’re getting so dehydrated,” Dr. Kavouras said.

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Persons: Kavouras, ”, Glen Kenny, aren’t, Kenny Organizations: University of Ottawa