May 8, 2007—The death toll from the F5 tornado that flattened tiny Greensburg, Kansas, last week has hit 10 and continues to rise, highlighting the danger of this powerhouse among twisters.
F5s can reach speeds of 261 to 318 miles an hour (420 to 511 kilometers an hour) strong enough to lift and carry entire houses.
In 1971, scientists adopted the Fujita scale of F1 to F6 to classify tornadoes. Wind speeds are estimated by surveying damage to buildings. Even the mild F1 can travel 73 miles (117 kilometers) an hour, damage chimneys, and uproot trees.
Watch footage from a twister's devastating path and see how researchers are working with radar to trace tornadoes before they hit.