If you’re prone to waking up sweat-drenched (or shivering) in the middle of the night, then you know how important it is to find your temperature sweet spot for sleep. But your body temperature does more than just keep you comfortable while you snooze—it’s actually a key part of what regulates the circadian rhythm that determines when your body is ready to go to sleep and when it’s ready to wake up.
The 98.6 degrees you likely think of as “normal” is actually just the starting point for your body’s internal temperature. From there, it fluctuates by a couple degrees over the course of the day—rising about one to two degrees from early morning until late afternoon, and then reversing until it hits its lowest point a couple hours before you wake up in the morning. When your temperature is on the rise, you’re most likely to feel alert and awake; when it’s falling, you’re likely to feel drowsy.
Since temperature is an such important part of determining when we fall asleep, it’s interesting that during rapid eye movement (REM) sleep, your brain’s temperature-regulating cells switch off and let your body temperature be determined by how warm or cool your bedroom is.
But that midnight chill isn’t necessarily a reason to pile on the blankets. Falling temperatures cue the onset of sleep, and may even help you sleep more soundly. In fact, wearing special clothing that lowers skin temperature by one degree Celsius can reduce middle-of-the-night arousals and early morning waking.
Chances are, you don’t have special cooling pajamas to further lower your skin temperature as you sleep, but taking a bath may have a similar cooling effect. It may seem counter-intuitive, since soaking in warm water initially raises your temperature. But remember, you ultimately have to get out of the tub. Doing so sets you up for a cool-down as you dry off and the water on your skin evaporates, and that sets the stage for sleep. Try to schedule this bath for 60 to 90 minutes before bed, so that your body temperature has a chance to drop before you jump into bed and pile on those cozy blankets. Otherwise, you might be too warm to rest comfortably!
And when you need help waking up in the morning (or you need to get out of an afternoon slump), consider doing some jumping jacks in place or going for a brisk walk to elevate your body temp—and your energy level.