Hailstones

Hailstones are a form of solid precipitation consisting of ice balls or irregular lumps that originate in thunderstorms. They form when updrafts in cumulonimbus clouds lift liquid water above the freezing level, where it freezes into ice. As the frozen particles are carried through the cloud by the updraft, additional layers of ice accrete around the core, producing stones with concentric growth. Hail often falls in bursts during severe convective storms and can occur wherever strong turbulence and sufficient moisture exist.

The growth of a hailstone depends on updraft strength, ambient temperature, and humidity. Stronger updrafts keep the stone aloft longer, allowing more ice to accumulate and producing larger stones. The internal structure reflects the storm’s temperature and moisture fluctuations, with alternating clear and cloudy layers forming during different growth periods. Hail sizes vary widely, from small pellets of less than a centimeter to large stones exceeding several centimeters in diameter; most hail is in the 1–2 centimeter range.

Hail is most common in mid-latitude regions that experience frequent strong thunderstorms, including the central United States, parts of South America, southern Africa, and sections of Asia and Europe. Severe hailstorms can cause property and crop damage, injure people, and affect transportation. Weather services monitor hail potential using radar and storm observations, issuing warnings to reduce risk and encourage protective actions.