Matt Jancer

Most parts of the Earth are getting hotter. Climate change and the heat island effect, where urban spaces trap heat, are making the warm seasons more brutal—sometimes dangerously so. This is the only planet we've got, at least until enough of us are living on Mars, so you may as well learn a few tricks on coping with the heat. 

Air-conditioning is still a luxury for many people, and even in the US and Canada it's not ubiquitous. Also, people trying to reduce their environmental footprint often choose to go without energy-sucking air conditioners, which raise city temperatures by pumping heat outdoors. Plus, the power could go out during an ill-timed heat wave. This guide has tips on how to stay cool when it's incredibly hot and air-conditioning is nowhere to be found.

Updated May 2021: We've fixed links and tweaked pricing throughout. 

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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, I deal with people suffering from heat exhaustion, and it's 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.

Heatstroke 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, and an extremely high body temperature (above 103 Fahrenheit), and they 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 water-soaked fabric to all four of the major artery areas—groin, both armpits, and back of the neck—and get help immediately.

Call a park ranger, call 911, call search and rescue—whichever is more applicable to where you are. Unlike heat exhaustion, where a person can recover and continue on given some time, heatstroke requires medical intervention.

If you're inside a building or a car, it's best to open two windows to get a cross-breeze flowing. If you have only one window open, fresh air entering is going to collide with hot air exiting, and your room isn't going to get much cooler. It's like people at movie theaters, where there are six doors but everyone is trying to simultaneously enter and exit through the same one. If you open two windows, the cooler outdoor air can enter more easily because the hot indoor air will be mostly exiting through the other window.

You can also place a fan near one of the open windows, facing outward so it's blowing hot air out of your room. If you don't have a good fan, we recommend this mountable, high-velocity Lasko floor fan ($78) and this Vornado floor fan ($70). Many home air purifiers also have adjustable fan settings that'll blow purified air on you.

You can try blackout curtains ($36) or thermal curtains. Yes, it'll be dark inside like a cave, but it'll also be cooler. Even regular curtains, which allow more light in, will reduce some heat as long as they're room-darkening and not sheer.

Another option is an evaporative cooler, such as this NewAir 300-square-foot model ($173). Evaporative coolers work by passing air over a water-soaked pad, which humidifies the air and lowers the room temperature. There are caveats, though. They work well only in dry environments. Even indoors, you generally have to live where the humidity is low to get the most out of these machines, although you can use them outdoors when the humidity isn't too high.

If you can handle the heat during the day but must have a cool bed at night, the BedJet 3 ($399) is a favorite of ours. It's pricey, though. If you're spending hundreds of dollars, you may just want to give in and buy a window air conditioner unit and find a closet for it the rest of the year.

You've got four major arteries on your body where the application of something cold or hot makes a great impact on your body temperature: your groin, armpits, and the back of your neck. The easiest one to chill is the back of your neck. Cool water is your friend, here, but even ambient-temperature water is better than nothing. 

When I was a kid, mowing the grass outdoors in North Carolina's brutal Piedmont summers, I used a Kafka's Kool Tie ($11) I borrowed from my father. Kool Ties are full of polymer crystals that absorb a lot of water, so one dip in a sink or under a hose spigot lasts for many hours. It works, although when it's really waterlogged it becomes quite heavy. It also bulks up and can reduce your head movement.

Another solution is a bandana. This $5 bandana by Carolina Manufacturing is what I've been using during the summer. Dip it in cool water, fold it into a triangle, and tie it so the broad part is over the back of your neck. Bliss. It won't get bulky, and you can stick it in a pocket later. Gear reviewer Parker Hall also swears by these Treadbands ($18). 

If you want a high-tech approach, try the Embr Wave 2 ($299) wrist band. It's unique in that it doesn't actually lower your body temperature; it lowers your perception of that temperature. If you're willing to shell out, know that it's more for alleviating some discomfort and won't work to keep your internal body temperature down in crazy-hot, grueling conditions.

You can easily sweat out 2 to 3 gallons of water in a day if it's particularly hot or you're active, so keep drinking. Sip constantly if you're finding it hard to stomach drinking big gulps. If your goal is survival against extreme heat, and you're not hiking long-distance where weight and bottle capacity are factors, check out our insulated water bottle picks for one that fits your needs. Drop some ice cubes in it and get drinking.

Early in the day, drink plain water. As you begin to sweat more heavily, switch to drinks containing electrolytes to replenish those you've sweated out: coconut water, Smartwater, Gatorade, and Powerade. Things like that. (Electrolytes are minerals in your body such as sodium and potassium that have an electric charge. They help balance your fluid levels.)

You could also try electrolyte tablets, like NUUN tablets ($7), and drop one in a bottle of plain water. Fruit smoothies are also a favorite of mine when the heat is killing me. Get something icy with a bit of coconut water, almond milk, and fruit solids to give you an energy boost and cool you down from the inside. Keep drinking them throughout the day to stay hydrated—small sips regularly, at least. And if your urine gets dark, it's time to up your intake.

Contrary to popular advice, coffee and soda are fine to drink. The amount of caffeine in them are low enough relative to the amount of water that they will still hydrate you if you're dehydrated. Beer is fine too, so long as it's a session beer (about 3 to 4 percent alcohol by volume) and not one with high ABV. Just pace yourself and don't drink too many of them. Studies that play up beer's diuretic effects—that is, it makes you urinate—tend to test with higher-ABV beers (5 percent or more) and on test subjects who are already well hydrated or hyper-hydrated. Even if that's the case, negative effects on your hydration would be close to negligible—unless you're hitting a lot of them or drinking those fancy, way-high ABV beers like barley wines and tripels.

Hard liquor is not a good idea. The alcohol content is too high relative to the overall volume of liquid in a serving.

You can pee clear and still be dehydrated. Plain water, on an empty stomach, speeds through the body. The digestive system recognizes that there are no nutrients to absorb from the water, and without food to digest—which requires water—the body gives it the green light to pass through the body as fast as it wants. It's like a high-occupancy-vehicle lane for fluids. It doesn't make chugging water useless—definitely keep drinking often since you are absorbing some of it. You'll just absorb more if there's food in your belly that will put the brakes on that flood of water, allowing your body to absorb more of it.

Any kind of food can help, from fresh oranges to a Snickers bar. But the best is salty food. Salt in your body helps absorb and hold onto the water you drink. My favorite snack when I'm climbing is those flavor-dusted pretzel nuggets.

Yes, drink water while you eat: There's been a persistent social media myth that you shouldn't drink water when you eat, but that's not true. You should definitely drink fluids while you eat.

If you're not hiking or working outdoors for a long period of time, shed layers. More exposed skin means more surface area for your sweat to transfer heat off your body. Take normal sun precaution, but if you're able to drink water or fluids, you may as well let the heat (and moisture) escape to feel cooler, since you can replace that moisture.

On the other hand, if your biggest concern is water retention, keep the sleeves and long pants on. You'll feel stuffy, but the fabric will trap the evaporated moisture off your skin, and if you're in direct sunlight, it'll cut down on sunburn. If you're sure you won't be under the sun that long, you can go for shorts or short sleeves.

Polyester and nylon clothes are the norm for hiking and camping situations where you're far from home or other indoor lodgings. Their appeal is that they dry out quickly, so you're less likely to end up soaked for hours and risk hypothermia as weather conditions change over your long trip. The problem is they tend to feel hotter than natural-fiber clothes, but it's often worth it.

Cotton feels cooler than nylon or polyester clothes. You generally shouldn't wear it in the wilderness, because it takes forever to dry out, and sweaty clothing becomes a threat if cooler weather rolls in or the temperature drops at night when you're stuck outside. There's a saying that "cotton kills," which means it elevates your risk for hypothermia in those situations. But if you're just working out in the yard or hanging around your home, go for cotton. You won't be at risk of hypothermia if you can go inside whenever you want.

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