It is unclear what you mean by "how long" a mile wide tornado produces damaging winds in a roughly circular diameter of one mile (1.6 km). Such large tornadoes tend to last longer than smaller ones, often more than half an hour.
The Xenia tornado of 1974 was about half a mile wide.
The path of a tornado is usually less than a mile wide, with most tornadoes ranging from 50 to 100 yards wide. However, some very large tornadoes are over a mile wide, and a handful of tornadoes have had paths over 2 miles wide.
It varies. The average tornado is 50 yards wind, but some are under 10 yards wide. Very large tornadoes can be up to a mile wide or more at the ground. The widest tornado ever recorded was 2.6 miles wide.
Thus Tuscaloosa-Birmingham tornado of 2011 varied in width, but at its maximum the tornado was about a mile and a half wide.
The widest tornado on record was 2.6 miles. The longest distance on record traveled by a tornado is 219 miles.
There is no specific type or rating for a tornado of a given size, though a mile wide tornado is likely to be very strong. The general term for a very large tornado (though not necessarily a mile wide), is "wedge."
The Tri-State tornado had a path of 219 miles long and 3/4 mile to 1 mile wide across 3 states and numerous mining towns.
The Tri-State tornado was a mile wide and traveled 219 miles.
The Waco tornado of 1953 was about one third of a mile wide.
The Joplin, Missouri tornado of May 22, 2011 tornado was 3/4 mile to 1 mile (1.2 to 1.6 km) wide.
The Waco tornado of 1953 was a third of a mile wide had a path length of 23 miles. Data does not appear to be available on how long it lasted.
The Flint, Michigan tornado of June 18, 1953 was about half a mile wide.
The Xenia tornado of 1974 was about half a mile wide.
Mile Wide Tornado Oklahoma Disaster - 2013 TV was released on: USA: 2 June 2013
The path of a tornado is usually less than a mile wide, with most tornadoes ranging from 50 to 100 yards wide. However, some very large tornadoes are over a mile wide, and a handful of tornadoes have had paths over 2 miles wide.
The Tri-State tornado was 3/4 mile to 1 mile wide along most of its path.
A tornado that stays on the ground for about 2 miles is common. The average path length is about 5 miles. However, a mile wide tornado is rare. The vast majority of tornadoes are well under a mile wide.