What You Tried: The cold makes us drowsy, and a falling core body temperature helps us drift off faster, says Nancy Collop, MD, director of the Bory Sleep Center in Atlanta. That's why you keep the bedroom cool—and also because previous experience (that non-air-conditioned cabin during a heat wave) has shown you that it's nearly impossible to fall asleep when you're sweating.
What You Should Try: Specialists usually give a ballpark suggestion of setting the thermostat to between 65 and 72 degrees—or that it feels just chilly enough so that you need a blanket. However, some cotton-blend sheets and pillowcases trap heat, as do memory foam mattresses. So you may doze off feeling snug, then wake up hot three hours later.
Keep Cool: There's an expanding range of products that claim to regulate your temperature while you sleep, including a brand-new line of cooling apparel from the bedding company Sheex. You could also set your air conditioner's timer to drop a few degrees in the middle of the night, or sleep with a fan.