Final answer:
Hail is most common in Colorado, but it can also occur in the Mississippi river valley.
Step-by-step explanation:
Hail is most common in Colorado. It is known for having a high frequency of severe thunderstorms, which often produce hail. The state's location in the central part of the country, along with its high elevation and proximity to mountains, contribute to the formation of hail.
While Colorado is the most common location for hail, it can also occur in other areas. The Mississippi river valley is another region that experiences a significant amount of hail due to its climate and proximity to the Gulf of Mexico.