During the summer, when the air is soft with humidity, your skin is unlikely to dry out even if you take multiple daily showers. So there’s no reason to choose between an evening or a morning rinse. You can enjoy both—and both have obvious appeal.

“A morning shower can help shake off sleep inertia and get you going, while an evening shower can be a relaxing part of a pre-bed routine,” says Michael Grandner, director of the Sleep and Health Research Program at the University of Arizona.

That may seem contradictory. How can the same activity both wake you up and help you get to sleep? The answer may have to do with how your body’s internal temperature helps control its circadian sleep rhythms.

Your core temperature naturally begins to drop in the evening and remains low while you sleep. (This is why many sleep experts caution against nighttime exercise: physical activity can raise your core temperature, and so forestall sleep.) While a shower before bed will briefly heat up your skin, you’ll quickly feel colder after toweling off because—as with sweat—the evaporation of skin moisture leads to skin cooling. This cooling effect may facilitate the onset of sleep, research has shown.

“A shower might also have the benefit of giving you some time to think and wind down before bed, rather than distract yourself in front of the TV,” Grandner says.

On the other hand, when you hop out of bed in the morning, a shower gets you on your feet and helps reinvigorate your senses. Since you’re likely to be on the move after your shower—headed to work, or to run errands—and your body’s circadian rhythms are driving your core temperature upwards, the shower won’t have the same soporific effect it does at night.

But sleep or wakefulness aside, there are other considerations.

Read it on instyle.com