Hail using rockets and artillery shells. Hail suppression programs have been undertaken by 15 countries between 1965 and 2005. Hail Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets fall generally in cold weather while hail growth is greatly inhibited during cold surface temperatures. Unlike other forms of water ice such as graupel, which is made of rime, and ice pellets, which are smaller and translucent, hailstones usually measure between
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