Hail forms in a complex dance between moisture and wind. Deep within cumulonimbus clouds ice crystals form and begin to fall towards the Earth’s surface. As this happens, wind gusts pick up the ice crystals, pushing them back up high into the clouds. As they begin to again fall down, they continue growing in size. Again, a wind gust might catch the growing hail stones, pushing them back up high into the clouds. This process may be repeated several more times until the hail stones become so large that they are too heavy for the wind to carry, causing them to fall towards the Earth.