It turns out that your brain and your body need to drop their core temperature by about one degree Celsius or around 2-3 degrees Fahrenheit to fall asleep and then to stay asleep, and this is the reason that you always find it easier to fall asleep in a room that is too cold than too warm. Therefore, the current recommendation is to aim for a bedroom temperature of about 65 degrees Fahrenheit or a little over 18 degrees Celsius. It sounds cool, but cool it should be.
Your body’s temperature decreases during sleep and a cool but not cold room will help you settle into and maintain sleep throughout the night.
I took this answer from the falling article. If you want to read more about optimal sleeping conditions, it offers you to read the entire short article.