Blankets and pillows on a bed.

There are many things that can hamper a good night’s sleep: late-night Netflix binges, inadequate exercise, a late-afternoon latte. But a hot bedroom can be one of the most frustrating.

For most people, optimal sleeping conditions are between about 60° F and 68° F, and 40 to 60 percent humidity. Anything outside these ranges, experts say, and sleep quality plummets. Multiple nights spent tossing and turning can leave you cranky and unproductive during the day, and over time poor sleep is tied to some serious health consequences. 

In the coming years, experts predict that—thanks to climate change—more heat waves will ripple across the globe with increasing intensity.

But with a few smart tips, you can transform an uncomfortably hot bedroom into something more tolerable, ensuring sounder slumber on even the warmest summer nights. (CR can help you find a mattress that retains less heat.)

The Perils of Poor Sleep

Few studies have looked into how sleeping in a hot room might affect your health, says Lauren E. Hale, Ph.D., a professor of family population and preventive medicine at Stony Brook University in New York and editor-in-chief of the journal Sleep Health. 

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But in general, scientists know that getting enough restorative sleep—in both time and quality—“is critical for the optimal functioning of every organ in the body,” Hale says.

Studies suggest that poor sleep is linked to weight gain and obesity, Hale says. After a bad night’s sleep, for example, people produce more of the hormone ghrelin, which makes them hungrier, and less leptin, a hormone that triggers the feeling of being full. “So a bad night’s sleep will affect your next day’s eating behavior,” she says, “which of course affects your weight.”

Other studies have linked long-term insomnia to an increased risk of high blood pressure, diabetes, cardiovascular disease, anxiety, depression, work and family problems, diminished quality of life, and even early death. 

Why Heat Can Make You Feel Beat

Your body temperature naturally fluctuates throughout the day, helping to regulate your internal clock, or circadian rhythm. When it rises, you tend to feel alert and awake, and when it falls, you tend to feel sleepy.

The ideal sleeping temperature differs from person to person, but in general, your body’s core temperature needs to drop for you to drift off at night. That slows down your metabolism and coincides with the release of melatonin, a hormone that makes you feel drowsy, sending a signal to your brain that it’s time to fall asleep. If your body is overheating at night, Hale says, it’s going to interrupt this process.

And a warm or muggy bedroom doesn’t just make it more difficult for you to cool down and fall asleep. It can make it harder to stay asleep, too. Some studies suggest that the discomfort of sleeping in a hot room can cause more frequent awakenings throughout the night and can disrupt restorative rapid eye movement (REM) sleep.

But the good news, experts say, is there are things you can do that can help—even if you don’t have air conditioning.  

How to Chill When It’s Hot Out

Block out the sun. If it’s hotter outside than inside, pull down the shades or close the blinds, and shut your windows, says Alcibiades Rodriguez, M.D., an assistant professor of neurology and medical director of the Comprehensive Epilepsy Center—Sleep Center at New York University’s NYU Langone Health medical center. That helps keep cool air in and hot air out. Closing the blinds has other benefits, too, because a dark room promotes a sounder sleep.

Cool down your room. Dial down the temperature and humidity in your bedroom with a window A/C unit or central A/C.

“If you aren’t fortunate to have those in your house or bedroom, then you can think about creating cross-ventilation,” Hale says. Open the windows (in the best-case scenario, more than one), and use a fan to circulate the air. If you have only one window in your bedroom, position a fan there so that it circulates the cooler nighttime air inside.

An added bonus of a fan, says Douglas Kirsch, M.D., president of the American Academy of Sleep Medicine, is that it provides white noise, “which often helps block other noises and improves sleep quality.”

An important note about fans, however: Public health agencies warn that using an electric fan in extremely hot conditions can be ineffective. The Centers for Disease Control and Prevention cautions that when temps are in the high 90s, a fan won’t be sufficient to prevent heat-related illness. 

And a new study in Annals of Internal Medicine found that a fan's effectiveness may be related to humidity—or the lack of it. When the researchers evaluated how well a fan cooled 12 healthy men, they found that the device was helpful in reducing heat stress in the study subjects when conditions were hot and humid. But in very hot, dry heat, using a fan actually raised the men's internal temperature and heart rate.

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Chill your bed. Try sealing your bedsheets and pillowcases in a plastic bag and sticking them in the freezer, Hale says. And to steer clear of overheating in your bed, avoid silk or polyester blended sheets; 100 percent cotton is best, according to the National Sleep Foundation, because it breathes better.

Some bed-cooling technologies, such as chilled mattress pads and toppers or cooling blankets, might also help, Kirsch says, though our experts at Consumer Reports haven’t tested them. And Kirsch says they might not be comfortable for everyone.

Choose a mattress that sleeps cool. If your bed-chilling attempts aren’t working, your mattress might be the problem. Some types, such as those made from foam, sleep warmer than others, such as innerspring mattresses.

With a Consumer Reports Digital Membership, you'll see below which mattresses have received high marks in our tests for keeping people cool and comfortable.

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Lower your body temperature. Taking a cold shower before bed can help lower your core body temperature and help promote sleep, Rodriguez says. You can also pat your bare skin with a damp towel or washcloth (while in your bed or just before you go to sleep), or try a cool compress on your forehead.

Stay hydrated. Warm temperatures make you thirsty, and getting out of bed for water disrupts sleep. Making sure you’re hydrated before you hit the hay and keeping a bottle or glass of water near your bed can minimize the need to leave your bedroom for middle-of-the-night water breaks, Rodriguez says.

Sleep solo. If you share a bed with your partner, that extra body heat can zap the quality of your sleep. Consider sleeping separately on really hot nights, Hale says. “That might have other benefits as well, if your partner snores or kicks,” she says.


How to Get a Good Night's Sleep

Not getting enough zzz's? "Consumer 101" TV show host Jack Rico gets expert CR tips on how to fall asleep faster and wake up more rested.

Editor's Note: Catherine Roberts contributed to this story.