Within those constraints, finding ways to stay hydrated and lower your body temperature are paramount. You can do this by drinking lots of fluids, wetting clothing or putting cold water or a cold rag on your hands, feet, armpits and neck. A portable handheld fan or a cooling vest can also help.

More than 37 million Americans are under heat advisories across the U.S., according to the National Weather Service. Here's the hardest hit areas.

A heat wave is moving in, with over 100 million people from the Midwest to the Northeast on alert for life-threatening heat this weekend and into next week.