Optimal Body Temperature During Sleep According to researchers, the optimal body temperature for sleep is about 65 degrees Fahrenheit, 2-3 degrees lower than average ambient room temperature. For those who prefer to slumber under a pile of blankets, even lower room temperatures are suggested — down to 60.5 degrees F. If our core temperature is too high the brain cannot easily make the switch from being awake to being asleep, or create the best quality sleep.