KNOXVILLE, Tenn. (WATE) — If you have ever seen frost in the morning, you’ve seen the impacts of radiational cooling. This is the cooling of the Earth’s surface.

During the day the sun is heating up the atmosphere, then at night when the sun goes away, surface temperatures start to drop. This is radiational cooling because heat is rising or radiating away from the surface, cooling it.

This happens faster when the skies are clear because clouds at night serve as a blanket trapping heat at the surface. When there isn’t cloud cover, temperature readings fall pretty fast and cooler overnight lows are seen.

Radiational cooling plays a role in frost development. ​If the cooling is forcing moisture onto the ground, and the air is at or below freezing, frost can form. The air right above the surface needs to be freezing or below, or under 32°F. The air higher up may be warmer, so long as the air right about the ground is at or less than 32°F.