Saffir-Simpson Scale

The USA uses the Saffir-Simpson hurricane intensity scale (Simpson and Riehl 1981) for the Atlantic and Northeast Pacific basins to give an estimate of the potential flooding and damage to property given a hurricane's estimated intensity:

Saffir-Simpson Scale for Hurricane Classification
Strength	Wind Speed (Knots)	Wind Speed (MPH)	Pressure (Millibars)	Damage
Category 1	65 - 82	74 - 95	>980	No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage.
Category 2	83-95	96-110	965-979	Some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of center. Small craft in unprotected anchorages break moorings.
Category 3	96-113	111-130	945-964	Some structural damage to small residences and utility buildings with a minor amount of curtain wall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain continuously lower than 5 feet ASL may be flooded inland 8 miles or more.
Category 4	114-135	131-155	920-944	More extensive curtain wall failures with some complete roof structure failure on small residences. Major erosion of beach. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet ASL may be flooded requiring massive evacuation of residential areas inland as far as 6 miles.
Category 5	>135	>155	<920	Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet ASL and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5 to 10 miles of the shoreline may be required.
Tropical Cyclone Classification
Tropical Depression			20-34 Knots
Tropical Storm			35-64 Knots
Hurricane			>64 Knots or 73 MPH

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