| F0 |
less than 73 mph |
Minor Damage |
| F1 |
73 to 112 mph |
Moderate Damage - Peels surface off roofs; windows broken; trailor houses pushed or overturned; trees on soft ground uprooted; some trees snapped; moving autos pushed off the road. |
| F2 |
113 to 157 mph |
Considerable Damage - Roof torn off frame houses leaving strong upright walls standing; weak structures or outbuildings demolished; trailor houses demolished; railroad boxcars pushed over; large trees snapped or uprooted; light-object missiles generated; cars blown off highway; block structures and walls badly damaged. |
| F3 |
158 to 206 mph |
Severe Damage - Roofs and some walls torn off well-constructed frame houses; some rural buildings completely demolished or flattened; trains overturned; steel framed hanger-warehouse type structures torn; cars lifted off the ground and may roll some distance; most trees in forest uprooted, snapped or leveled; block structure often leveled. |
| F4 |
207 to 260 mph |
Devastating Damage - Well-constructed frame house leveled, leaving piles of debris; structure with weak foundation lifted, torn, and blown some distance; trees debarked by small flying debris; sandy soil eroded and gravels fly high in the wind; cars thrown some distance or rolled considerable distance finally to disintegrate; large missiles generated. |
| F5 |
261 to 318 mph |
Incredible Damage - Strong fram houses lifted clear off foundation and carried considerable distance to disintegrate; steel-reinforced concrete structures badly damaged; automobiles-sized missiles fly through the distance of 100 yards or more; trees debarked completely; incredible phenomena can occur. |
| F6 |
319 to 379 mph |
Inconceivable Damage - Large objects such as storage tanks and automobiles will fly through a long distnace; home foundations ripped from ground. Assessment of tornadoes in these categories is feasible only through detailed survey involving engineering and areodynamical calculations as well as meteorological models of tornadoes. |
| F7 - F12 |
380 mph to the Speed of Sound |
Not expected to occurr! |
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National Weather Service Forecast Office