Is climate change making hailstones larger?
The last two years were record years for large hail reports. Could a warming climate mean bigger hailstones?
To understand how oddly-shaped hail happens, you first have to understand how hail forms. AccuWeather’s Anna Azallion explains.
Statistics show an increase in the number of large hailstones in the United States over the past two years, which has caused meteorologists and researchers to wonder: Is hail getting larger, and if so, is climate change to blame?
Hail develops when rising air in a thunderstorm, known as the updraft, lifts water droplets high into the atmosphere where temperatures are below freezing.
Before hailstones become too heavy to fall to the ground, the updraft pushes them up repeatedly, freezing more ice around them. The stronger the storm, the more powerful the updraft, resulting in larger hailstones.
Hail is classified by diameter, from pea size, one-quarter of an inch across, to softball size, 4 inches across. One hailstone that fell in Texas on April 28, 2021, set a new state record at 6.4 inches in diameter, and Colorado set its state record with a 5.25-inch stone that fell on Aug. 8, 2023.
A hailstone that fell in Vivian, South Dakota, on July 23, 2010, holds the United States record for the largest size with a diameter of 8 inches and heaviest weight at 1.94 pounds.
2023 and 2024 set new records for 3 different months
As of May 5, 2025, the Storm Prediction Center (SPC) has tallied 332 storm spotter reports in the United States of hail larger than 2 inches in diameter (a golf ball is 1.75 inches), according to the Iowa Environmental Mesonet (IEM). It was an active April, ranking number 3 since 2004.
The summer of 2023 was a blockbuster hail season, with 540 reports of hailstones 2 inches or larger in June and 305 in July, both new records for those months that exceeded previous records by more than 200 percent.
The top six days with the most 2-inch or higher hail reports since 2006 occurred in 2023 and 2024, with 106 reports on March 14, 2024, a new record.
In 2024, a new record of 144 reports was set for March, then 541 reports were received in May, besting the previous record of 351 in 2011.
Both 2023 and 2024 also set new records for 2-inch hail reports for the entire year.
These stats have meteorologists asking whether large hail is becoming more common.
Hail measurement is an inexact science
Large and extreme hailstones have always fallen on the Plains but were not well documented until the mid-2000s. One important thing to remember about spotter network data is that more spotters lead to an increase in reports over time. More storm chasers trying to document the largest hailstones could account for some of the recent upswing, but June 2023 and May 2024 remain outliers.
Because documenting hail size is difficult, only nine states maintain official records on hailstones. Other inconsistencies can also call the data into question.
Hail can melt quickly before a measurement can be taken. Spotter reports can be estimated. Although oblong conglomerations of hailstones can have a large diameter, they may weigh less than other round stones of a similar diameter.
(NOAA)
Will hailstones get larger as a result of a warming Earth?
Because hail formation is a complicated process, few studies have examined whether a warming world produces larger hailstones or more days with hail. The IPCC warns that there is "low confidence in observed trends in tornadoes and hail because of data inhomogeneities and inadequacies in monitoring systems."
One of the only studies on this subject was conducted in 2017 and was based on a computer model forecast in a warming climate.
The paper's hypothesis was that increasing temperatures should lead to more thunderstorms with strong updrafts, which would lead to more—or larger—hailstones. However, they found that this was not necessarily true because higher temperatures could also melt small hail before it reaches the ground.
Hail size changes for 2041-2070 vs. 1971-2000 in spring and summer. (Nature: 10.1038 / NCLIMATE3321)
The paper concluded that hail size is expected to increase, noting, "Although fewer hail days are expected over most areas in the future, an increase in the mean hail size is projected, with fewer small hail events and a shift toward a more frequent occurrence of larger hail."
The study's figures show that the 30 years between 2041 and 2070 would produce fewer hail days and smaller hailstones compared to the 1971-2000 period for states on the East Coast of the United States. However, both measures would increase in the central Plains, Rockies and Canada.
Change in hail days, 2041-2070 vs. 1971-2000, for Spring and Summer. (Nature: 10.1038 / NCLIMATE3321)
