The National Weather Service has safety tips for adults looking to keep cool.
Slow down. Try to reduce or cancel any strenuous activities, or reschedule them for the coolest part of the day.
Wear lightweight, light-colored clothing to reflect sunlight and heat.
Eat lighter foods. Meat and other proteins increase metabolic heat production and could cause even more water loss.
Drink plenty of water, but avoid alcohol and caffeinated drinks.
Spend more time in air-conditioned places. If you don't have an air-conditioner in your home, go to a library, store or other location for part of the day to stay cool.
Avoid getting too much sun. Sunburn can reduce your body's ability to release heat.
ABC News' Matt Gutman, The Associated Press and ABC News Indiana affiliate WRTV-TV and Chicago affiliate WLS-TV contributed to this story.