The summer can be dangerous, and doctors say it's important to be alert to signs of overheating or hyperthermia.
Early on, you might notice cramping, but that can quickly move to heat exhaustion and heat stroke, which can be deadly.
Doctors say make sure you're hydrated before you go outside to work, play or train.
"So that when they lose fluids in sweating and things, that they don't lose as much, and they want to replace those as they're doing the activity," described Dr. Linda Mansfield of Memorial Sports Medicine in South Bend. "So, hydrating during the activity is a key component to preventing some of these things."
Dr. Mansfield says people with heat distress can start to lose their judgment, so watch out for those around you, and get them into a cool place.
The hot weather can especially pose a special risk to children and older people.