Hail Reports

Imagine a baseball dropped from an airplane flying at 30,000 feet ... imagine that baseball reaching speeds of 120 MPH as it falls to the ground ... and imagine you're under it!

Photo from
National Center for Atmospheric Research

Imagine you're driving along at 70 MPH...or your crops are under the hail producing thunderstorm...or your home is under the thunderstorm...
Hail causes $1 billion in damage to crops and property each year

Credit: NOAA Photo Library, NOAA Central Library

The costliest hailstorm in the United States was in Denver in July 1990 with damage of $625 million.
Even small hail can cause significant damage to young and tender plants

Credit: NOAA Photo Library, NOAA Central Library

How does hail form?

Inside of a thunderstorm are strong updrafts of warm air and downdrafts of cold air.
If a water droplet is picked up by the updrafts...it can be carried well above the freezing level. With temperatures below 32F...our water droplet freezes.
As the frozen droplet begins to fall...carried by cold downdrafts...it may thaw as it moves into warmer air toward the bottom of the thunderstorm
But...our little half-frozen droplet may also get picked up again by another updraft...carrying it back into very cold air and re-freezing it. With each trip above and below the freezing level our frozen droplet adds another layer of ice.
Finally...our frozen water droplet...with many layers of ice - much like the rings in a tree...falls to the ground - as hail!

NOAA image

How large can hail get?
Fortunately...most hail is small - usually less than 2 inches in diameter
The largest hailstone ever recorded fell in Coffeyville, Kansas on September 3, 1970. It measured about 17.5 inches in circumference (over 5.6 inches in diameter) and weighed more than 26 ounces (almost 2 pounds)!

Credit: NOAA Photo Library, NOAA Central Library

Hailstones can begin to melt and then re-freeze together - forming large and very irregularly shaped hail

Is there a way to estimate hail size...or do I have to go outside and measure it?

It's often difficult to get an accurate measurement of hail diameter - especially when it's falling
The table to the right helps observers estimate the size of hail based on average diameters of common items
When in doubt - play it safe and wait until the thunderstorm has moved away before going outside to measure the size of hail

Estimating Hail Size

Pea = 1/4 inch diameter

Marble/mothball = 1/2 inch diameter

Dime/Penny = 3/4 inch diameter - hail penny size or larger is considered severe

Nickel = 7/8 inch

Quarter = 1 inch

Ping-Pong Ball = 1 1/2 inch

Golf Ball = 1 3/4 inches

Tennis Ball = 2 1/2 inches

Baseball = 2 3/4 inches

Tea cup = 3 inches

Grapefruit = 4 inches

Softball = 4 1/2 inches