RAPID CITY, S.D. (KEVN) On July 23, 2010, thunderstorms developed over central South Dakota. Many storms became severe and one in particular moved over portions of Stanley, Jones and Lyman Counties. One of the hardest hit locations was Vivian, South Dakota, where extremely large hail, damaging winds up to 80 mph and even a brief tornado.
One hail stone in particular in Vivian, shattered multiple records. The hailstone was measured to be 8.0" in diameter. To put into perspective of how large that is, the diameter of a volleyball is 8.15". this particular hailstone was also 18.625" in circumference and weighed an incredible 1.9375 pounds!
This hailstone broke the previous United States hail size record for diameter (old record was 7.0" on June 22, 2003 in Aurora, NE) and weight (old record was 1.67 pounds on September 3, 1970 in Coffeyville, KS). The Aurora Nebraska hailstone previously mentioned still holds the record for circumference at 18.75".
Something to note, the hailstone's official record dimensions were as of the time NWS employees from Aberdeen first observed and measured it. The stone did shrink considerable by melting and sublimation between impact and when it was first measured. There were many other hailstones with diameters exceeding 6" with this storm during the survey!