Hail stones start as water drops. A strong wind updraft blows the drops up above the freezing level in the clouds and the drops freeze. When they get heavy enough, they fall. When they fall, one of three things can happen; the hail stone will melt and fall as rain, the hail stone won’t melt and will fall as a hail stone or the updraft will be strong enough to blow the hailstone back above the freezing level and the stone will get bigger.
Boy Scout Weather Merit Badge 