History of Hail in Timeline

Hail is a form of solid precipitation consisting of ice balls or irregular lumps called hailstones, differing from ice pellets. Hail formation is hindered by low surface temperatures, which generally is the opposite for ice pellets. The distinction between hail and ice pellets lies in their formation and conditions under which they occur. Hail is typically associated with thunderstorms where upward drafts of air repeatedly lift water droplets into freezing layers of the atmosphere, which causes them to accumulate ice and eventually fall to the ground when they become too heavy.

1965: Start of hail suppression programs

From 1965, hail suppression programs have been undertaken by 15 countries.

2005: End of hail suppression programs

By 2005, hail suppression programs have been undertaken by 15 countries since 1965.

January 2010: US National Weather Service Hail Diameter Threshold Increase

In January 2010, the US National Weather Service increased its hail diameter threshold to 1 inch (2.5 cm), up from the previous threshold of 0.75 inches (1.9 cm).

July 29, 2010: Foot of Hail Accumulation in Boulder County, Colorado

On July 29, 2010, a stationary thunderstorm caused a foot of hail to accumulate in Boulder County, Colorado.

June 5, 2015: Four Feet of Hail in Denver, Colorado

On June 5, 2015, hail up to four feet deep fell on one city block in Denver, Colorado, with hailstones between the size of bumble bees and ping pong balls.

2023: Hailstorm Damage Costs in the United States

In 2023, hailstorms in the United States resulted in $46 billion in damage to cars, roofs, and crops, according to the Insurance Institute for Business & Home Safety (IBHS).

2025: ICECHIP Field Study Begins

In Spring 2025, the "In-situ Collaborative Experiment for Collection of Hail In the Plains" (ICECHIP), the world's largest field campaign devoted to studying hail, began in the United States to study hail processes in thunderstorms, involving 100 scientists from four countries and 11 states.