Force 0: Light Damage

Less than 72 mph (116 kph) - Damage to chimneys and billboards; broken branches; shallow-rooted tress pushed over.

Force 1: Moderate Damage

73 to 112 mph (116 to 180 kph) - The lower limit is near the beginning of hurricane wind speed. Surfaces peeled off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the road.

Force 2: Considerable Damage

113 to 157 mph (181 to 253 kph) - Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated.

Force 3: Severe Damage

158 to 206 mph (254 to 332 kph) - Roofs and some walls torn off well-constructed homes; trains overturned; most trees in forest uprooted; heavy cars lifted off ground and thrown.

Force 4: Devastating Damage

207 to 260 mph (333 to 419 kph) - Well-constructed houses leveled; structures with weak foundations blown some distance; cars thrown and large missiles generated.

Force 5: Incredible Damage

Greater than 260 mph (419 kph) - Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized missiles fly through the air farther than 100 meters; tress debarked; incredible phenomena occur.

Lutgens, Frederick K., and Edward J. Tarbuck, 1998. The Atmosphere. Simon and Schuster: Upper Saddle River, New Jersey. 434 pgs.