A South Dakota hailstone nearly 8 inches wide still holds the US record for size

Les Scott stepped outside his home in Vivian, South Dakota, after a thunderstorm passed on July 23, 2010, and found a hailstone nearly the size of a bowling ball sitting in his yard. He stored it in his freezer, and when officials measured it days later it came in at 8 inches in diameter, 18.62 inches in circumference and a pound and 15 ounces, a stone the National Weather Service still lists as the largest ever recovered in the United States.

A freezer, a power outage and a race against melting

Scott told the National Weather Service office in Aberdeen that the stone he found had already begun to shrink; by his account, other hailstones nearby had been even larger when the storm first ended. “Mr. Scott told me the area was littered with large hailstones and the largest had a greater diameter when he first found it,” said David Hintz, the warning coordination meteorologist at NOAA’s Aberdeen office. “He immediately stored it and several others in his freezer, but a power outage caused some melting.”

Scott’s own reaction, recorded at the time by the weather office, focused less on the record than on the storm that produced it: he said he was simply glad no one had been hurt and hoped the town would recover soon. Personnel from the Aberdeen weather office drove out to measure and weigh the surviving stone before submitting it to NOAA’s National Climate Extremes Committee, the three-member panel responsible for certifying national weather extremes. The panel reviews photographs, field measurements and chain-of-custody notes the same way it would for a temperature or rainfall record, a process that in Vivian’s case stretched from July into a formal certification issued that November.

Wet growth, dry growth and how a stone gets that big

Hailstones start as raindrops carried into the coldest part of a thunderstorm by its updraft, where they freeze around a speck of dust or ice and then keep colliding with supercooled water droplets on the way back down, and up again, inside the storm. When a stone freezes quickly it traps air bubbles and turns cloudy; when it freezes more slowly, in what NOAA’s National Severe Storms Laboratory calls “wet growth,” trapped air escapes and the layer comes out clear, which is why a cut hailstone often shows rings like a tree trunk marking each pass through the storm. Meteorologists have sliced open recovered stones for decades specifically to count those rings, since the number of clear-and-cloudy pairs roughly tracks how many times a given hailstone rode the updraft back up before finally falling.

Meteorologists treat 2 inches in diameter as the threshold for “severe” hail, a size NSSL associates almost exclusively with supercell thunderstorms, whose rotating, sustained updrafts can hold a stone aloft long enough to add layer after layer. The Vivian stone was roughly four times that severe-hail threshold, which meant the supercell that produced it had to sustain an updraft strong enough to suspend nearly two pounds of ice, an unusually long-lived balancing act even by supercell standards.

A record that survived sixteen years of bigger storms

NOAA’s National Climate Extremes Committee certified the Vivian stone as the U.S. record for both diameter and weight, surpassing a 7-inch stone recovered in Aurora, Nebraska, in 2003 and a 1.67-pound stone from Coffeyville, Kansas, in 1970. Wikipedia’s own entry on hail lists the diameter as 7.9 inches, a figure derived from the metric measurement of 20 centimeters rather than the 8.0-inch figure NOAA’s field team recorded directly, a small discrepancy that has followed the record through repeated retellings without changing which storm, or which stone, holds it.

No hailstone recovered in the United States since 2010 has matched Vivian’s for diameter, even as Tornado Alley and the central Plains have produced a stream of severe hailstorms in the years since. Insurers have felt that trend regardless of any single record: the Insurance Institute for Business & Home Safety calculated that hailstorms cost the United States $46 billion in damage to vehicles, roofs and crops in 2023 alone, a cost driven far more by the sheer frequency of two-inch-and-larger hail across populated areas than by any stone approaching Vivian’s size.

Vivian sits roughly 30 miles south of Pierre, the state capital, in a stretch of central South Dakota that sees some of the country’s most consistent severe-hail conditions each summer, yet no storm crossing that same ground in the years since has produced a stone NOAA has certified as bigger. The National Climate Extremes Committee’s final memorandum on the case runs to several pages of measurement notes and comparison photographs, the kind of paperwork usually reserved for a record temperature or a record flood, applied instead to a piece of ice that had already started melting in a chest freezer before anyone official arrived to look at it.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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