Frost is a frozen dew. Dew is the little drops of water you sometimes see on leaves and grass. Dew freezes on cold nights when there are no clouds and no wind. If there were clouds they would act like a blanket, keeping the earth warm. If there were wind, warm and cold air would get mixed up, and it might not get cold enough to make frost.
The frost that forms on misty windows is called fern frost.
1. Frost can form on airplane wings while planes are flying up high where the air is cold. This can be dangerous, so airplanes have special equipments to get rid of the ice.
2. Long ago, the weather was much colder in winter than it is now. Rivers froze solid, and people got together and had markers and fairs on the ice.