History of Hail in Timeline

Hail is a form of solid precipitation, characterized by balls or irregular lumps of ice called hailstones. It is often confused with ice pellets, but the two differ; ice pellets typically fall in cold weather, while hail growth is hindered by low surface temperatures. Hail forms when strong updrafts in thunderstorms carry water droplets into extremely cold areas of the atmosphere. These droplets freeze and collide with other supercooled water and ice crystals, accumulating layers as they are repeatedly lifted and fall within the storm cloud. Eventually, the hailstones become heavy enough to overcome the updraft and fall to the ground.

1965: Start of Hail Suppression Programs in Multiple Countries

Beginning in 1965, numerous countries initiated hail suppression programs.

2005: Ongoing Hail Suppression Programs

By 2005, 15 countries were still actively engaged in hail suppression programs.

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: Hail Accumulation in Boulder County, Colorado

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

June 5, 2015: Deep Hail Accumulation in Denver, Colorado

On June 5, 2015, hail up to four feet deep fell on one city block in Denver, Colorado, accompanied by rain and high winds.

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 Hail Study Launch

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, commenced in the United States. The study involves 100 scientists from multiple countries, researching hail processes in thunderstorms across the Great Plains and the Colorado/Wyoming Front Range.