Hail, fog, dew, and frost are all forms of precipitation. Precipitation is any form of water that falls from the atmosphere and reaches the ground. This includes rain, snow, sleet, hail, dew, and frost. Hail is formed when frozen water droplets are lifted by strong updrafts in thunderstorms, while fog is formed when water vapor in the air condenses close to the ground. Dew forms when moisture condenses on cool surfaces, and frost forms when the temperature drops below freezing and water vapor in the air freezes directly onto surfaces.