Precipitation Precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, rain, sleet, snow, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates". Thus, fog and mist are not precipitation but suspensions, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with
Ice pellets a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL (PE before November 1998). Ice pellets are known as sleet in the United States, the official term used by the U.S. National Weather Service. However, the term sleet refers to a mixture of rain and snow in most Commonwealth countries, including Canada. Because of this, Environment Canada never uses the term "sleet", and uses the terms "ice pellets" or "wet snow" instead. Ice pellets form when a layer of above-freezing air is located between above the ground, with sub-freezing air both above and below