Definition
A form of solid precipitation consisting of balls or irregular lumps of ice, formed in strong thunderstorm updrafts that repeatedly carry water droplets above the freezing level, where they accumulate successive layers of ice before falling to the ground.
Plain English
Chunks of ice that fall from thunderstorms. They form when strong rising air inside the storm lifts water drops high enough to freeze, then keeps tossing them up and down until they grow heavy enough to fall.
Context Anchor
Seen in weather briefings, thunderstorm forecasts, pilot reports, and decisions about avoiding storm cells.
Derivation
From Old English 'hagol,' meaning small stones of ice falling from the sky. The everyday meaning and the aviation meaning are the same — the term has not drifted.
Why Pilots Care
Hail can dent or penetrate aircraft surfaces, damage windshields, and cause engine ingestion problems, creating a serious safety risk.
Grounding Statement
Picture small ice stones being thrown out of a thunderstorm and striking the airplane at flight speed.
Intuition Check
Hail is not just a winter weather problem. If a thunderstorm is strong enough, hail can form and fall even in warm weather.
Example Sentence 1
The crew diverted around the line of thunderstorms after a PIREP reported hail at their cruising altitude.
Example Sentence 2
Hail damage was discovered on the leading edges during the postflight inspection.