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In much the same way as raindrops form around a nucleus, so hail forms around graupel or ice crystals. Supercooled water droplets accumulate on the crystal as it is carried upwards on a rapidly rising column of air within a towering cumulonibus cloud. Large hailstones can be held aloft for up to 10 minutes, carried up and down within a cloud before finally achieving a fall speed greater than the updraft to fall as hailstones.

With particularly large hailstones it is possible to count the layers and thus the number of times the hailstone has been carried up through the cloud. Oddly, hail is most likely during hot summer months as the warmer moisture-rich air rises dramatically to greater heights, cooling rapidly. The heaviest hailstones on record weighed more than 1kg each and killed 92 people in Gopalgang, Bangladesh on 14 April 1986.