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Why does or how can frost form... | Almanac.com

Why does or how can frost form...

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Why does or how can frost form when temperature is above freezing?
Answer
Moisture collects on surfaces on clear nights with little or no wind. When the temperature dew point is below freezing, water vapor changes directly to frost instead of first condensing as dew. Also, the ground retains the coolness necessary to freeze moisture longer than the surrounding air.