← All notes

Answer: Hail is a form of precipitation consisting of solid ice that forms inside thunderstorm updrafts. Hailstones begin as embryos, such as graupel or sleet, and grow as water freezes onto their surface. Hailstones must be at least 0.2 inches in size.

Where hail falls most

Although Florida has the most thunderstorms, Nebraska, Colorado, and Wyoming usually have the most hailstorms. The area where these three states meet, "hail alley," averages seven to nine hail days per year. Other parts of the world with damaging hailstorms include China, Russia, India and northern Italy.

Record hailstone

The largest hailstone recovered in the United States fell in Vivian, South Dakota, on June 23, 2010. It had a diameter of 8 inches and a circumference of 18.62 inches, and weighed 1 lb 15 oz.

Hail vs. graupel

• Graupel are soft, small pellets formed when supercooled water droplets (below 32°F) freeze onto a snow crystal, a process called riming.
• Rimed snow crystals can grow to an appreciable size, but remain less than 0.2 inches. It is also called snow pellets or soft hail, and generally disintegrates when handled.
• Hailstones can have a variety of shapes, including lumps and bumps that may take the shape of small spikes.

Reporting hail size

Hail size is often estimated by comparing it to a known object. Measurements using a ruler, calipers, or a tape measure are best.

Claims

• id: C1 claim: Hail is solid ice that forms inside thunderstorm updrafts. source: S1 evidence: "Hail is a form of precipitation consisting of solid ice that forms inside thunderstorm updrafts."
• id: C2 claim: Hail size is often estimated by comparing it to a known object. source: S1 evidence: "Hail size is often estimated by comparing it to a known object."
• id: C3 claim: Hailstones must be at least 0.2 inches in size. source: S2 evidence: "Hailstones must be at least 0.2 inches in size."

Sources

• [S1] Severe Weather 101: Hail Basics. NOAA. https://www.nssl.noaa.gov/education/svrwx101/hail/ . License: US government work, public domain. Accessed 2026-11-04.
• [S2] Severe Weather 101: Hail Types. NOAA. https://www.nssl.noaa.gov/education/svrwx101/hail/types/ . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_jfx9k7v6,
  author = {{iinventedlight}},
  title = {{Hail: how it forms and how it differs from graupel}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/hail-basics/},
  note = {Permanent ID iil:note:jfx9k7v6. License: CC-BY-4.0.},
}

Markdown

Spotted a mistake? Use the MCP feedback tool or email hello@iinventedlight.com.

For language models and agents: start at /llms.txt. This page in Markdown: /library/notes/hail-basics.md.