In an average year, hail causes more than $1.6 billion worth of damage to residential roofs in the United States, making it, year in and year out, one of the most costly natural disasters. Hailstorms are most frequent in the southern and central plains states, where warm moist air off of the Gulf of Mexico and cold dry air from Canada collide, thereby spawning violent thunderstorms. This region, known as hail alley, lies predominantly within the states of Texas, Oklahoma, Colorado, Kansas, Nebraska, and Wyoming. While their domain of greatest frequency is in the plains states, hailstorms have been observed just about everywhere thunderstorms occur.

The combination of gravity and a downward wind known as a downburst (a common occurrence during severe thunderstorms) can propel a hailstone at speeds upwards of 90 mph. At such excessive speeds, large hailstones have been known to penetrate straight through roof coverings and the deck to which they are attached. Although the majority of hailstorms are not quite so severe, even moderate hailstorms can damage buildings, automobiles, crops, and other personal property.