High temperatures can wreak havoc on sleep. Under ideal conditions, your body temperature starts to fall by a couple of degrees about one to two hours before bedtime in preparation for sleep — and it continues to decline while sleeping, said Leslie Swanson, a clinical psychologist and associate professor of psychiatry in the Sleep and Circadian Research Laboratory at the University of Michigan. This internal cooling effect helps us achieve the deep, restorative stage of sleep known as slow-wave sleep.
But “when the ambient temperature is high outside, it prevents our body temperature from falling as quickly to where we want it to be in order to facilitate sleep,” Dr. Swanson said. This not only makes it harder to fall asleep, but it can also cause frequent awakenings during the night.
While it may be difficult to drift off when both you and your room are warm, there are things you can do to snooze more soundly.
Do what you can to cool down your bedroom. “We tend to get more deep sleep in a cool bedroom,” said Philip Gehrman, a clinical psychologist at the Penn Sleep Center at the University of Pennsylvania. He even noted that “for some people, once summer hits and they crank up the A/C, they sleep better because they’re keeping their bedroom cooler than they would in spring or fall.” (Wirecutter, a New York Times Company that reviews and recommends products, has tips for keeping a room cool on a budget.)
Get the air in your room moving. If you don’t have access to air conditioning, use a fan to help the air circulate in your room. Increasing the airflow across the surface area of your body helps to offload heat, said Dr. Justin Fiala, a pulmonary critical care and sleep medicine specialist at Northwestern Medicine.
Stay hydrated. If you can’t lower the temperature of your room your body will turn to another method for cooling you down: sweating. Keep some water by your bedside to make sure you can replenish the liquid you’re losing. “You’re actually going to lose a lot of your water volume just through sweat,” Dr. Fiala said.
Use lightweight bedding. Though you might be tempted to forego any sort of blanket in the hot weather, the best way to help your body regulate its temperature is to use a light sheet or summer comforter, Dr. Fiala said. Make sure it’s one you can easily move around under, though, so you can still kick out your foot or another limb to help cool down.
Avoid a cold shower right before bed. While dousing in cold water will help your body lower its temperature, it likely won’t help you with the quality of your sleep. “It has not been shown to be effective and it can somewhat be stimulating,” Dr. Fiala said. Cold water can be a shock to the body, which might keep you awake for longer.