Plain English Meaning

Lumps of ice that form inside thunderstorms and fall from the sky. They can be anywhere from pea-sized to bigger than a golf ball, and they can seriously damage an airplane.

Full Definition

Solid pieces of ice that form inside thunderstorms when supercooled water droplets freeze onto a nucleus and are carried up and down through the storm by strong updrafts, accumulating layers of ice until they grow heavy enough to fall to the ground. Hailstones range in size from small pellets to several inches in diameter and can cause severe damage to aircraft structures, windscreens, and engines.

Context Anchor

Seen in thunderstorm and severe-weather discussions, weather briefings, and decisions about avoiding storm cells.