The Enhanced Fujita scale took effect in the United States in 2007, specifically on February 1.
It replaced Ted Fujita’s original Fujita scale, which had been used since 1971. The revised system was designed to connect tornado damage more consistently with estimated wind speeds. It added standardized damage indicators, degrees of damage, and greater attention to construction quality.
The changeover can cause confusion because tornadoes that occurred before February 1, 2007, retained their original F-scale ratings, while later U.S. tornadoes were rated EF0 through EF5. The first tornadoes classified under the new system struck central Florida on February 2, 2007; they included EF3-rated tornadoes.
The EF scale still estimates intensity from damage rather than directly measuring every tornado’s peak wind. Its highest category, EF5, has no stated upper wind-speed limit.