Hail is a form of solid precipitation. It is distinct from American sleet (called ice pellets outside of the United States), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Sleet (ice pellets) falls generally in cold weather while hail growth is greatly inhibited during cold surface temperatures. Unlike graupel, which is made of rime, and ice pellets, which are smaller and translucent, hailstones consist mostly of water ice and measure between 5 millimetres (0.2 in) and 15 centimetres (6 in) in diameter. The METAR reporting code for hail 5 mm (0.20 in) or greater is GR, while smaller hailstones and graupel are coded GS. Hail is possible within most thunderstorms as it is produced by cumulonimbi, and within 2 nautical miles (3.7 km) of the parent storm. Hail formation requires environments of strong, upward motion of...