Why is it get so cold right 1 or 2 hours before sunrise ? If you sleep outside, under a clear sky, and its starts to get really cold, you know sunrise isnt far anymore.
Actually i just figured it out. In the night when the warm air is flowing into space, there is still a little belly of warmer air around the ground. Then when sun rises a few kilometres away, from the place i am, the sun starts to warm that air and the air expands, and stirs up. So the cold air from above stirs up and gets mixed with the warmer air on the ground, and thats why it gets so cold around the ground. And this mixing air comes also to the place where sun will rise in 1 to 2 hours. Its like a nature clock. But when its a cloudy night, you might not feel an temperature drop down, because the clouds are reflecting the warm air and only a little bit goes out into space.