The widest tornado ever recorded by the National Weather Service was 2.6 miles in diameter. It occurred in El Reno, Okla., in 2013. Tornadoes this wide are quite rare, as it is difficult for tornadoes to sustain their momentum as they grow.
Researchers don't know enough about tornadoes to accurately predict how wide a tornado could possibly be. The width of tornadoes can only be measured indirectly, either by measuring the width of the destructive track left by the tornado or by analyzing meteorological data that can be inconclusive. There is no official measurement for the length or speed of a tornado. The Enhanced Fujita scale, which ranks tornadoes from 0 to 5, only takes into account the damage caused by the storm.