The water droplets attach themselves to the ice pellets and begin to freeze as strong updraft winds toss the pellets and droplets back up into the colder regions of the upper levels of the cloud. As the attached droplets freeze, the pellets become larger. Both gravity and downdraft thunderstorm winds pull the pellets back down, where they encounter more droplets that attach and freeze as the pellets are thrown, once again, back up through the cloud. The more times a hailstone is tossed up and down through the cloud, the larger the hailstone will be. Hailstones the size of softballs had many more trips up and down through the cloud than pea-sized hailstones.
Large hailstones are an indication of powerful updraft and downdraft winds within a thunderstorm.
This is why large hail is associated with severe thunderstorms. The largest hailstone ever measured in the United States fell at Coffeyville, Kansas, on September 3, 1970. It weighed 1.67 pounds and measured 17.5 inches in circumference. The Great Plains states, especially northeastern Colorado and southeastern Wyoming, receive more hail yearly than any other part of the United States. Hail in this area of the country is most likely to fall late in the afternoon during the months of May and June and is often responsible for extensive crop loss, property damage and livestock deaths.