A hailstorm is a storm that produces hail: chunks of ice that fall from the sky like frozen rain. Unlike regular raindrops or soft snowflakes, hailstones are solid balls or lumps of ice that can range from the size of a pea to as large as a grapefruit (though most are closer to marble-sized).

Hailstorms form when strong updrafts in thunderclouds carry raindrops high into freezing air. The drops freeze, then get tossed up and down through the cloud, collecting more layers of ice with each trip, like rolling a snowball. Eventually they become too heavy for the wind to hold up, and they plummet to Earth.

These storms can be surprisingly destructive. Large hail can dent cars, shatter windows, damage roofs, and flatten crops in minutes. Farmers dread hailstorms during the growing season because a single storm can destroy an entire field of wheat or corn. In hail-prone regions like the American Great Plains, some people build special carports or use hail-resistant roofing materials.

Hailstorms can also be dangerous to people and animals, because even small hailstones can hurt when they hit, and larger ones can cause serious injuries.