As adults, we no longer get three months off for a summer break, but there's something about this time of year that just begs you to take things easy. And what's easier than a midday nap? You know the drill: you've been reading in the backyard or laying by the pool—maybe you've just come in from the heat and plopped down in your favorite chair. Your body is relaxed. Your eyelids are heavy and you slip into a blissful state of sleep because, well, it's summer and you can.

After all, napping is a universal rite of life when the weather's warm. The siesta is common in a number of Mediterranean, tropical and subtropical countries as a way to take a break from the scorching midday heat. What's more, the siesta habit has been associated with a 37 percent reduction in coronary mortality in those countries, possibly due to reduced cardiovascular stress mediated by daytime sleep. According to Dr. Sara Mednick, a leading sleep scientist and author of Take a Nap! Change Your Life, napping not only benefits your heart, but also boosts brain activity, speeds cell repair and lowers stress.

So don't fight the feeling when that familiar drowsiness hits you after lunch. Succumb to the indulgence of letting yourself fall asleep in the middle of the day. Do it outside with a hat over your face and get a little vitamin D. Or curl up in the cool calmness of a well-air-conditioned space. Whatever you do, don't sweat the lack of productivity. Because in the end, your body's better of for getting the extra sleep. And the unplanned, easygoing nature of a nap is the ultimate summer luxury. The kind that doesn't cost you a thing.