This set of pages was developed and written by Brian Dunneback, a University of Illinois Department of Geography student.
Tornadoes are one of nature's most destructive phenomena.
Scientists define tornadoes as, very simply, violently rotating columns of air. Tornadoes form in severe weather, from large anvil-shaped clouds called cumulonimbus clouds. Tornadoes come in different shapes and sizes. They can reach up to speeds of over 300 miles per hour. Tornadoes track through Illinois at a rate of just over 29 per year.