Hail this size sounds almost fictional until you see the photos: chunks of ice the size of a volleyball, falling at well over 100 km/h, punching holes through decking and leaving craters in the ground. The US holds several of these outright records, and interestingly, they aren't all held by the same storm.
The biggest by diameter and weight: Vivian, South Dakota, 2010
On 23 July 2010, a severe supercell thunderstorm moved through Stanley, Jones and Lyman counties in central South Dakota, producing destructive winds up to 80 mph, a brief tornado, and hail large enough to make national news. A resident of the tiny town of Vivian, population under a hundred, collected several of the giant stones and stored them in a freezer. When National Weather Service meteorologists from Aberdeen examined the largest one, it measured 20.3cm, exactly 8 inches, in diameter, and weighed 0.88kg, just under 1.94 pounds. Both figures set new US records, and the hailstone had already lost roughly 3 inches of its original size to melting before it could be measured, thanks to a storm-caused power outage that put the freezer out of action for hours.
The storm that produced it was genuinely extreme even by supercell standards: NWS analysis put the updraft speeds required to support a hailstone that size at somewhere between 160 and 180 mph. For context, hail generally has to be held aloft inside a storm's updraft long enough to add successive layers of ice before it becomes too heavy to stay airborne, which is exactly why the biggest hailstones only come from the most violent, sustained updrafts on Earth.
The Vivian stone broke two separate previous US records in one go. Its diameter beat the previous record of 17.8cm (7 inches), set in Aurora, Nebraska, on 22 June 2003. Its weight beat the previous record of 0.76kg (1.67 pounds), set in Coffeyville, Kansas, on 3 September 1970.
The one record Vivian didn't take
Despite setting new marks for diameter and weight, the Vivian hailstone does not hold the US record for circumference. That distinction still belongs to the 2003 Aurora, Nebraska hailstone, which measured 47.6cm (18.75 inches) around, very slightly larger than Vivian's 47.3cm (18.625 inches). It's a reminder that "biggest" isn't a single number: a hailstone's shape, especially if it's irregular or lobed rather than a clean sphere, means diameter, weight and circumference don't always track together, and different storms have ended up holding different pieces of the record depending on exactly how their hail grew.
For scale
The Vivian hailstone is also recognised as the heaviest ever recorded anywhere in the Western Hemisphere, according to the World Meteorological Organization. The global weight record belongs to a hailstone that fell in the Gopalganj district of Bangladesh on 14 April 1986, weighing 1.02kg (2.25 pounds), part of a storm that tragically killed 92 people, a stark reminder that hail this size isn't just a curiosity but a genuine hazard.