Hail is a large frozen raindrop produced by intense thunderstorms, where snow and rain coexist. As the snowflakes fall, liquid water freezes onto them, forming ice pellets that will continue to grow as more and more droplets accumulate. Upon reaching the bottom of the cloud, some of the ice pellets are carried by the updraft back up to the top of the storm. As the ice pellets once again fall through the cloud, another layer of ice is added and the hail stone grows even larger. Typically the stronger the updraft, the more times a hail stone repeats this cycle and consequently, the larger it grows. Once the hail stone becomes too heavy to be supported by the updraft, it falls out of the cloud toward the surface. The hail stone reaches the ground as ice, since it is not in the warm air below the thunderstorm long enough to melt before reaching the ground.

Hail might seem like a minor concern, but it can shatter windows, leave pockmarks in siding and destroy or damage roof coverings. Hail causes $1 billion in damage to crops and property each year. Even small hail can cause significant damage to young and tender plants. The costliest hailstorm in the United States took place in Denver in July 1990 with damage of $625 million.
 

The Power of Hail

To understand the power of hail imagine a baseball dropped from an airplane flying at 30,000 feet ... imagine that baseball reaching speeds of 120 MPH as it falls to the ground ... and imagine you're under it!
 

The Largest Hailstone

How large can hail get? Fortunately, most hail is small -- usually less than two inches in diameter. The largest hailstone ever recorded fell in Coffeyville, Kansas, on September 3, 1970. It measured about 17.5 inches in circumference (over 5.6 inches in diameter) and weighed more than 26 ounces (almost 2 pounds)!