The Enhanced Fujita scale is a tornado category scale used to measure tornadoes in the United States and Canada by how bad their damage is. The National Weather Service started using it on February 1, 2007 and in Canada in April 2013. The weakest tornadoes on this scale are classified EF0, and the strongest storms are classified EF5. The scale replaces the old Fujita scale in America. Tornadoes under EF5 label represent winds of 200 miles an hour or stronger. No tornadoes in the United States that happened before February 1, 2007 will have their ratings changed to the new scale.