Temperatures are climbing around the globe. Record heat has been cooking large swaths of the U.S. as well as Europe and China, and the hottest part of summer is still ahead. For most people, that means much more time spent as a sweaty, sticky mess.
“We’re seeing the hottest summers in recorded history, multiple years in a row,” says Dr. Grant Lipman, an emergency physician and founder of the Global Outdoor Emergency Support (GOES) Health app. “This is an issue for all different demographics and walks of life.”
Being really hot can be unpleasant and irritating; research has linked high temperatures to aggression and violence, as well as worse life satisfaction. It can also be dangerous: Extreme heat is one of the leading causes of weather-related deaths in the U.S. each year, claiming about 158 lives per year nationwide over the past 30 years.
Here’s what to know about why the heat bothers some people more than others, and the most effective ways to cool down fast.
How the body regulates heat
The human body regulates heat in a few different ways: by vaporization (in other words, sweating); radiation, or releasing heat into the surrounding air; convection, which occurs when you’re enveloped by cooler air (which is why air conditioning is so effective); and conduction, or transferring body heat onto cold water or ice.
Some people are more susceptible to heat than others, usually depending on their environment, physiology, and prior exposure to heat, says Heather Massey, a senior lecturer in clinical exercise physiology and member of the Extreme Environments Laboratory at the University of Portsmouth in the U.K. “Particularly if you’re more aerobically fit, and if you regularly expose yourself to increased body temperature through exercise, you may be better acclimatized to a warmer environment or having a body temperature that’s elevated,” she says.
If you’ve spent a lot of time in a cold environment, however, you may find the transition into heat more challenging. After several days of being exposed to warm weather, “most people start to adapt,” Massey notes. “But if you’re in and out of air conditioning all the time, that might be problematic.”
It’s possible to train for better heat tolerance, Lipman says, and it usually takes about a week for your body to start adapting and finding better ways to cool itself. For example, if you’re planning to hike the Grand Canyon, where you know it will be scorching, Lipman recommends exercising in warm weather for an hour or two a day for about 10 days leading up to the activity. During that time, “your body’s reaction starts becoming more resistant to heat stress, in the sense that you’re able to shed heat quicker,” he says.
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Being aware of the temperature and humidity throughout the day and planning accordingly can help prevent heat illness, Lipman says. He and other experts emphasize these safety strategies that people should use when the temperature hits about 85 degrees Fahrenheit or above. (Since heat tolerance is individual, some people will be extra susceptible to lower temperatures.)
Avoid exercising at certain times. Heat tends to peak during the afternoon, so plan your outdoor activities in the morning. Dr. Jennifer Bontreger, a sports medicine specialist in Highland Village, Texas, coaches the athletes she works with to practice in the early morning. It also usually gets cooler in the evenings.
Dress right. Prioritize light, loose clothing with built-in UV protection, advises Amy Acton, a former nurse who’s CEO of the non-profit Phoenix Society for Burn Survivors. (People with severe burns often lose their ability to sweat, which means survivors are prone to heat exhaustion and heatstroke and have to be extra careful in the sun.) “There’s so much happening in textiles and fabrics these days to help us stay cool,” she says. “The science behind that has come a long way.” Look for clothing with an ultraviolet protection factor (UPF) of at least 30; that will help prevent some of the sun’s rays from penetrating the fabric. According to the Skin Cancer Foundation, UPF 50 blocks 98% of the sun’s rays, greatly reducing the risk of sun damage and skin disease.
Start your day well-hydrated. If you’re thirsty—and especially if you become dehydrated—“you’re not going to be able to sweat as much as you possibly can,” which means you won’t cool down as efficiently, Massey says. Make a point to stay hydrated, and if you’ve been exercising outdoors, drink about as much as you lost in sweat plus a little more, she advises.
Electrolyte-enhanced drinks can be helpful in the heat, Bontreger says, since electrolytes help prevent heat-related cramping. Plus, she adds, alcohol and caffeine can dehydrate you, so it’s best to steer clear of those on hot days.
Be smart about events. In general, avoid scheduling or attending outdoor gatherings from around 10 a.m. to 4 p.m., unless there’s ample shade, says Wendell Porter, a senior lecturer emeritus in agricultural and biological engineering at the University of Florida. Otherwise, “Somebody’s going to get in trouble,” and it’s never fun when festivities dissolve into emergencies. Even playing a lawn game like cornhole could ramp up a vulnerable person’s metabolic rate, Porter says, making them more susceptible to heat, so it’s best to proceed with extra caution when it’s very hot outside.
If you’re feeling ill, get out of the sun. Look for a shady spot or head indoors if you start experiencing symptoms such as heat cramps, a headache, or excessive sweating, Lipman says. It can take an hour or so until you return to your baseline. And if you suspect heatstroke—which includes symptoms like nausea and vomiting, a rapid pulse, fainting, confusion, or seizure—call 911 right away.
The most effective ways to cool down fast
Some cooling-off methods work better than others. Here’s what experts suggest when you’re hot and unable to rely on air conditioning:
Spray yourself with water. In the Extreme Environments Laboratory, which researches the best ways to enhance comfort, performance, and survival under harsh conditions, Massey has learned that spraying yourself with cool tap water and then fanning yourself (with your hands or a piece of paper, or by standing in front of a fan) is a particularly effective way to promote cooling. “It simulates sweating on the skin, and then evaporation and convective cooling of the skin,” she says. This strategy can also work well for those who don’t have access to air conditioning.
While water works well, Massey advises skipping menthol-based cooling sprays, which are packaged like sprayable sunscreen and designed to provide the skin with the sensation of cooling. These sprays might make your skin feel cooler, but they don’t lead to deep-body cooling, she says—and that could put you in a dangerous position, if you believe you’ve cooled down but actually haven’t. In that case, you might continue working or exercising outside, but since your body hasn’t cooled down, you’ll be at greater risk of heat illness.
Soak your hands and feet. The extremities are “amazing radiators of heat, especially when we’ve got an elevated deep body temperature,” Massey says. Often, children like going to the restroom to wash their hands in cold water—and they have the right idea. Even reasonably cool water will do the trick, she notes; it doesn’t need to be ice-cold.
Douse your clothes with water. It’s not always practical, but if you’re sweltering, figure out a way to dampen your clothes, Lipman suggests. One way to accomplish that: run through a sprinkler, just like you did when you were a kid.
Keep a supply of ice packs in the freezer. Ice packs work, Massey says: you can press one on your cheeks, hands, or feet. But there are downsides to consider. In addition to advanced planning—so that you always have one when and where you need it—ice packs will eventually melt, so there’s a time stamp on their helpfulness. (It’s also best not to put ice packs directly on your skin; keep a thin layer of cloth, like a shirt or rag, in between to avoid skin damage.)
Some people invest in ice vests, which are typically made out of cooling fabric with inserts for ice sheets. If you don’t find them too uncomfortably heavy, they can be helpful. Craig Crandall, director of the Thermal and Vascular Physiology Laboratory at the Institute for Exercise and Environmental Medicine, knows a burn survivor who wears one for outdoor activities. “She’ll play soccer with these cooling vests on to help keep her cool, and it does work,” he says.
If someone is showing signs of heatstroke, submerge up to half their body in cold water. This is considered the gold standard for rapidly cooling someone who has heat illness, Lipman says. Lower the person into water (perhaps a tub, kiddie pool, or lake) up to their armpits for about 10 minutes. “The colder the better—even if someone starts to shiver, the cold water will cause a temperature gradient and allow them to shed heat quicker,” he says.
Capture the cool air indoors. Even on a blisteringly hot day, there will be relatively cool spans of time—usually from around 3 to 7 a.m., Wendell says. Aim to get as much of that cool air into your house as possible by keeping the windows open and blinds open. “Then, right when the sun comes up, close your house up,” he says. Consider investing in blackout curtains, which will reduce the amount of heat that’s transferred inside via your windows.
In homes without AC, Wendell also recommends taking a cold shower before bed, running a cool cloth over your head, and, if possible, staying with a friend or family member when it’s uncomfortably hot. Fans can be helpful, but in the interest of saving electricity, always turn them off when you leave a room. “A fan only cools you,” he says. “It evaporates the moisture on your skin, but it doesn’t do a thing for the room.”
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