A tornado is a spinning, tube of air. They touch both the ground and a cloud. Sometimes a tornado is called a twister. Most tornadoes have wind speeds less than 100 miles per hour. Some extreme tornadoes have winds up to 300 miles per hour. Most tornadoes travel only a few miles before they lift back into the cloud. The Tri-State tornado occurred in 1925. It traveled 219 miles and killed 695 people. It was the deadliest tornado in U.S. history.