Why Do Freezers Frost?

Frost in a freezer occurs when warm, moist air meets with the cold temperature inside the freezer.


The moist air freezes, creating tiny ice crystals that adhere to the cold surfaces inside the freezer.

Leaving the freezer door ajar creates frost quickly inside a freezer. A cracked or damaged door seal also creates frost because the warmer air surrounding the freezer seeps in and freezes.

Humidity Level

A high humidity level inside the room where the freezer is located creates frost due to the high moisture level in the air.

Normal Build-Up

Some build-up of frost is normal in freezers that aren't self-defrosting. Manually defrost the freezer according to the manufacturer's instructions when the build-up measures 1 inch thick.

Freezer Temperature

Freezers should be kept at or below 0 degrees F. While frost forms easily at this temperature, colder temperatures create frost more quickly because the outside air freezes faster when it enters the freezer.

Frost-Free Freezers

Frost-free freezers operate differently than regular freezers, and should not have frost. If frost is present, it may be due to a broken evaporator fan, a broken defrost heater, a plugged drain line, or a broken defrost timer.

About the Author

Maelin McCartney began writing professionally in 2010. She holds undergraduate degrees from Hastings College in health and developmental psychology, family studies psychology, personality and social psychology and sociology with an emphasis in criminal justice. She is currently pursuing a master’s degree in counseling at Doane University.