The Largest U.S. Hailstone Was 8 Inches Across

On July 23, 2010, thunderstorms developed over central South Dakota, and the community of Vivian was one of the hardest hit. The U.S. National Weather Service reports that a record setting hailstone was discovered there, measuring 8.0 inches in diameter and 18.625 inches in circumference, and weighing 1.9375 pounds. It broke the previous United States records for diameter, which was 7.0 inches, set in Aurora, Nebraska, in 2003, and for weight, which was 1.67 pounds, set in Coffeyville, Kansas, in 1970. The Aurora stone keeps the record for circumference. The measurements may understate the stone. The Weather Service notes that the official dimensions are those taken when its staff first observed and measured it. It was not alone, either. Many other stones with diameters exceeding 6 inches were noted during the storm survey.