Rain and snow mixed and snow. Though no "official" criteria exist for the term, in the United Kingdom the term is not used when any significant accumulation of snow on the ground takes place. It is often used when the temperature of the ground surface is above , preventing accumulation from occurring even if the air temperature is marginally below ; but even then, the falling precipitation must generally be something other than exclusively snow. In the United States, wintry mix generally refers to a mixture of freezing rain, ice pellets, and snow. In contrast to the usage in the United Kingdom, in the
Hail with air, wind, and interaction with rain and other hailstones can slow their descent through Earth's atmosphere. Severe weather warnings are issued for hail when the stones reach a damaging size, as it can cause serious damage to human-made structures and, most commonly, farmers' crops. Any thunderstorm which produces hail that reaches the ground is known as a hailstorm. Hail has a diameter of or more. Hailstones can grow to and weigh more than . Unlike ice pellets, hailstones are layered and can be irregular and clumped together. Hail is composed of transparent ice or alternating layers of transparent and