Hail is like rain made out of little pieces of ice. These little ice lumps fall out of storm clouds in a thunderstorm. They may already be molten when they reach the ground, but sometimes they stay frozen little balls.
How do hailstones form?
Hailstones form within huge thunder clouds (see Thunder & Lightning. Little very cold watrer drops get whirled around it thunderclouds and while they whirl around they come in contact with other cold water drops. If the cloud is quite warm (for a thundercloud, that means above -14° Celsius), "wet", clear and sometimes very large hailstones get formed. If the temperature withing the cloud is lower than -14° Celsius, only small water and ice pieces attach themselves to the hailstone and the hailstones are less clear and have little air compartments in them. This is calles "dry" growth of hailstones. Because the hailstones get whirled around a lot in the cloud and continue to partly melt and freeze again, some hailstones look like they are built with different layers. Next time you see a hailstorm, take one of the pieces and see if it is clear or not clear. This will tell you how cold the cloud it came from was!
Size of hailstones
Hailstones can be very small, but sometimes they are 4 times as big as eggs. If they are that big, houses, cars, people and animals can be damaged or hurt because the hail can be very hard and heavy.
Damage by hailstones
In May 2000 a hail storm caused great damage in Illinois in the USA. Golfball-, baseball-, and softball-sized hail damaged roofs, cars, patio furniture, skylights, and windows. Around 100,000 homes lost power. The hailstones were up to 3 inches deep. A lot of flights were cancelled because of it.
