It’s hot this summer, and Earth seems to just keep getting hotter. Until Elon Musk takes us to Mars, it’s the only planet we’ve got. Depending on where you live, you may or may not have (or feel you need) air conditioning, and sometimes it fails. Or maybe you’re planning to go on a hike or be outside for an extended period of time.

This guide has some tips on what to do when it’s incredibly hot and that blessed AC is not there to chill you out.

Signs of Heat Exhaustion and Heat Stroke

Whether you’re indoors or out, heat can sneak up on you if you aren’t careful.

Heat exhaustion is a culmination of overheating, dehydration, and other factors overloading the body’s cooling system, which causes a lot of problems. People in the grip of heat exhaustion can be combative and confused.

As a Wilderness First Responder, dealing with people suffering from heat exhaustion is one of the toughest parts of the role, because they often don’t want to be helped. I bump into a lot of people suffering from it on hiking trails, climbing routes, and kayaking launch points. I try to get them to sit down, sip cool water, and nibble a salty snack. People love free snacks. And smiles.

Heat stroke is an escalation of heat exhaustion that goes on for too long. A person with this is in serious danger, and someone needs to act immediately to save their life. They usually have hot, red skin, a rapid, strong pulse, an extremely high body temp (above 103 Fahrenheit), and are usually too mentally checked out to fight you about anything. They could also be unconscious or so out of it that they won’t accept food or water. Sit them down in the shade, apply cool-soaked fabric to all four of the major artery areas—groin, both armpits, and back of the neck—and get them help immediately.

Call a park ranger, call 911, call search and rescue. Whichever is more applicable to where you are. Unlike heat exhaustion, where given enough time to recover a person could continue on once they’re feeling better, heat stroke requires medical intervention.

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