Hailstorms are a product of severe thunderstorms. Hail is formed when strong updrafts within the storm carry water droplets above the freezing level, where they remain suspended and continue to grow larger, until their weight can no longer be supported by the winds. Hailstones can vary in size, depending on the strength of the updraft.

The National Weather Service (NWS) uses the following descriptions when estimating hail sizes: 

Pea size is ¼-inch	Quarter size is 1-inch
Marble size is ½-inch	Golf ball size is 1 ¾-inches
Dime size is ¾-inch	Baseball size is 2 ¾-inches

Individuals who serve as volunteer "storm spotters" for the NWS are located throughout the state, and are instructed to report hail dime size hail (¾-inch) or greater. Hailstorms can occur throughout the year, however, the months of maximum hailstorm frequency are typically between May and August. Although hailstorms rarely cause injury or loss of life, they can cause significant damage to property.  On average, northeastern Minnesota is subject to a hailstorm only once a year.  

Hailstorms are a common occurrence, but damage is typically minimal and related to roofs, siding, and vehicles. A hailstorm in the summer of 1998 caused significant damage to siding and roofs in Duluth with an estimated damage of $50 million. Duluth Township experienced golf ball sized hail in 1994.  A total of 139 hail events have been recorded for St. Louis County between 1950 and 2003 according to the National Climate Center database. This is an average of 2.6 hailstorms annually.