Ask the 6 Storm Team: How frost forms

KNOXVILLE (WATE) – A common misconception is that frost is frozen dew or frozen rain, but that is not the case. Frost is actually water vapor that forms different shapes of ice, by passing the liquid stage and freezing into a solid.

It’s a layer of ice that forms on surfaces that are at or below 32 degrees Fahrenheit. Sometimes frost can occur on your lawn overnight, even though your thermometer may never have dropped to the freezing mark.

You’ve seen it before early on a crisp fall or winter morning. It looks like freshly fallen snow but it’s actually frost. This is because cold air on clear, calm nights sinks to ground level. Temperatures at the ground can be lower than the temperature only a few feet higher where your thermometer may be located.

For example, the temperature could be three to four degrees warmer near my neck and near freezing on the ground at the same time. Frost would likely form on objects 32 degrees or colder.

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