How Does Frost Form?

Frost is frozen dew, so frost formation depends on both humidity and temperature. Under the right conditions, a super-cool layer of air can form very close to the ground. At the same time, the air temperature 4-6 feet above the ground can be 5-10° warmer. If the ground air temperature is below 32°, dew will fall from the warm air and freeze as frost in that super-cool air. So “frost warnings” start whenever the temperature is expected to be within a few degrees of freezing, especially on damp nights. Plants’ leaves may brown and blooms fall off after a frost, but it is when plants freeze that annuals actually die. A “hard freeze” occurs when air temperatures drop low enough to freeze the water within the plant tissue. For more information, check out Meteorologist Lauren Rautenkranz explaining frost for her Florida viewers.