Your body’s internal temperature begins to cool down before you go to bed. That’s one reason why some sleep experts recommend taking a bath or shower before bed, will naturally cool of afterward, signalling to your body that it’s time to go to sleep. Later in the night, thought during REM sleep, your body cant’s regulate its own temperature, and for the most part, people tend to be in the REM stage of sleep right around dawn when temperatures are . So we naturally learn that even if it’s pretty hot when we go to bed, we’ll wake up shivering at 4 a.m if we don’t have a blanket. There are psychological reasons to cover up too. When you’re baby, your parents put blankets on you when you sleep, so you’re conditioned throughout your early years to associate blankets Above all, maybe we just all want to be swaddled forever. Doesn’t that sound nice?