Thunderstorms originate in cumulonimbus clouds. Warm, humid air rises then cools, creating moisture to form the cloud. Thunderstorms produce heavy rain, strong winds and sometimes hail.
There are three main types of thunderstorms. Orographic thunderstoms are formed by air traveling up a hill or mountainside. Frontal thunderstorms form around the outskirts of weather fronts. Air mass thunderstorms are caused by localized convection in an unstable air mass.
Thunderstorms are most likely to occur during the spring and summer, but they can occur at any time of the year. A common thunderstorm is 15 miles across and lasts about 30 minutes. Thunderstorms can happen anywhere, and all produce lightning.