Category F0: Gale tornado (40-72 mph); light damage. Some damage to chimneys; break
branches off trees; push over shallow-rooted trees; damage to sign boards.
Category F1: Moderate tornado (73-112 mph); moderate damage. The lower limit is the
beginning of hurricane wind speed; peel surface off roofs; mobile homes pushed off
foundations or overturned; moving autos pushed off the roads.
Category F2: Significant tornado (113-157 mph); considerable damage. roofs torn off
frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or
uprooted; light-object missiles generated.
Category F3: Severe tornado (158-206 mph); Severe damage. Roofs and some walls torn
off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars
lifted off ground and thrown.
Category F4: Devastating tornado (207-260 mph); Devastating damage. Well-constructed
houses leveled; structure with weak foundation blown off some distance; cars thrown and
large missiles generated.
Category F5: Incredible tornado (261-318 mph); Incredible damage. Strong frame houses
lifted off foundations and carried considerable distance to disintegrate; automobile sized
missiles fly through the air in excess of 100 yards; trees debarked; incredible phenomena will