CNN —Thunderstorms can bring dangerous lightning, heavy rain, strong winds and sometimes ice stones falling from the sky – known, of course, as hail. Hail forms when warming at the Earth’s surface causes water to evaporate and rise, eventually reaching freezing temperatures higher in the atmosphere. Hail formation can be broken into two types: wet growth or dry growth, according to the National Weather Service. The new formations then fall and freeze together relatively slowly, which can give hail interesting shapes depending on how the pieces combine. Since freezing isn’t immediate during wet growth, air bubbles can escape, which makes these hailstones partially clear.

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