Origins
The word 'hail,' referring to frozen precipitation, descends from Old English 'hagol' or 'hΓ¦gl,' froβββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββm Proto-Germanic *haglaz, with cognates in German 'Hagel,' Dutch 'hagel,' Old Norse 'hagl,' and Gothic 'hagl.' The Proto-Germanic form traces to PIE *kaΗ΅hlo-, meaning 'pebble' or 'small stone.' The metaphor is direct: hailstones are pebbles from the sky. Greek 'kΓ‘khlΔx' (ΞΊΞ¬Οληξ, a round pebble on a beach) is cognate.
This 'hail' is entirely unrelated to the greeting 'Hail!' and the verb 'to hail' (to call out to, to greet). The greeting comes from Old Norse 'heill' (whole, healthy, hale), from PIE *koylo- (whole, uninjured) β the same root that produced 'whole,' 'health,' 'heal,' 'hale,' and 'holy.' The weather word and the greeting are homonyms by coincidence: they converged in spelling and pronunciation through the separate sound changes of English history, but their PIE roots are different.
Hail forms inside cumulonimbus clouds β the tall, towering thunderstorm clouds that can reach heights of 15 kilometers or more. Updrafts within these clouds carry water droplets upward into regions of extreme cold, where they freeze. The frozen particles then fall, accumulate more water, are lofted again by updrafts, freeze another layer, and repeat. Each cycle adds a layer of ice, like the layers of an onion. When the hailstone becomes too heavy for the updraft to support, it falls to the ground. Cutting a large hailstone in half reveals concentric rings of clear and opaque ice β clear ice from slow freezing (which allows air bubbles to escape) and opaque ice from rapid freezing (which traps air).
Development
The largest authenticated hailstone on record fell in Vivian, South Dakota, on 23 July 2010: it measured 20.3 centimeters (8 inches) in diameter and weighed 879 grams (1.94 pounds). Hailstones this large fall at over 160 km/h and can smash through car windshields, destroy roofs, and kill people and livestock.
In the runic alphabet (the Futhark), the h-rune was named *Hagalaz (hail). In the Old English Rune Poem, the hail-rune is described: 'Hail is the whitest of grains; it comes from high in the air, is whirled by the wind, and turns to water.' The rune was associated with disruption and destructive natural forces.
Hail damage is one of the most costly forms of weather-related destruction. In the United States alone, hail causes billions of dollars in damage annually, primarily to crops, vehicles, and roofing. The corridor of the Great Plains from Texas to South Dakota β sometimes called 'Hail Alley' β experiences the highest frequency of large hailstorms in the world, due to the unique combination of strong updrafts, moisture from the Gulf of Mexico, and cold air from Canada.