Hail is possible within most thunderstorms as it is produced by cumulonimbus clouds within two nautical miles (3.7 km) of the parent storm.
Hail formation requires environments of strong, upward motion of air with the parent thunderstorm (similar to tornadoes) and lowered heights of the freezing level. Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0 °C.
Here's a list of hail records from around the world:
- Heaviest: 1.02 kg (2.25 lb); Gopalganj District, Bangladesh, 14 April 1986.
- Largest diameter officially measured: 7.9 inches (20 cm) diameter, 18.622 inches (47.3 cm) circumference; Vivian, South Dakota, 23 July 2010.
- Largest circumference officially measured: 18.74 inches (47.6 cm) circumference, 7.0 inches (17.8 cm) diameter; Aurora, Nebraska, 22 June 2003.
- Greatest average hail precipitation: Kericho, Kenya experiences hailstorms, on average, 50 days annually. Kericho is close to the equator and the elevation of 7,200 feet contributes to it being a hot spot for hail. Kericho reached the world record for 132 days of hail in one year.
Watch the video below for some of the most powerful hailstorms caught on tape.