Meteorologists say a deadly tornado in North Dakota this summer has been upgraded to a top-of-the-scale EF5, and was the first on American soil in 12 years. The June 20 twister killed three people and at its largest was over a mile wide as it touched down for just over 12 miles. Meteorologists from the National Weather Service estimated Monday that the tornado had winds in excess of 210 miles per hour. The 1999 Bridge Creek-Moore tornado in Oklahoma holds the record of the strongest winds ever recorded in the U.S. at 321 miles per hour. Since the National Weather Service began using Enhanced Fujita scale in 2007, there have been 10 tornadoes categorized as EF5.