what does it refers to?
Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet")
Hail
Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"),
what time of year is hail most likely In North America it occurs between  March and October,with the bulk of the occurrences from May through September.
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Hail [SEP] Introduction
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 and in diameter. The METAR reporting code for hail or greater is GR, while smaller hailstones and graupel are coded GS.