Category 1 [Minimal] Damage primarily restricted to shrubbery, trees, and  unanchored mobile  homes; no substantial damage to other structures; some damage to poorly constructed signs low lying roads inundated; minor damage to piers; small craft in exposed  anchorages torn from moorings.

Category 2 [Moderate] Considerable damage to shrubbery and tree foliage, some trees blown down; major damage to exposed mobile homes; extensive damage to poorly constructed signs and some damage to windows, doors and roofing materials of buildings, but no major destruction to buildings coastal roads and low lying escape routes inland cut off by rising water about 2 to 4 hours before landfall; considerable damage to piers and marinas flooded; small craft in protected anchorage torn from moorings evacuation of some shoreline residences and low lying areas required.

Category 3 [Extensive] Foliage torn from trees; large trees blown down; poorly constructed signs blown  down; some damage to roofing, windows, and doors; some structural damage to small buildings; mobile homes destroyed. serious flooding along the coast; many small
structures near the coast destroyed; larger coastal structures damaged by battering waves and floating debris low lying escape routes inland cut off by rising water about 3 to 5 hours before landfall; flat terrain 5 feet or less above sea level flooded up to 8 or more miles  inland evacuation of low lying residences within several blocks of shoreline may be
required.

Category 4 [Extreme] Shrubs, trees, and all signs blown down; extensive damage to roofs, windows, and doors, with complete failure of roofs on many smaller residences; mobile homes demolished flat terrain 10 feet or less above sea level flooded inland as far as 6 miles;
flooding and battering by waves and floating debris cause major damage to lower floors of structures near the shore; low lying escape routes inland cut off by rising water about 3 to 5 hours before landfall; major erosion of beaches massive evacuation of all residences within 500 yards of the shore may be required, as well as of single story residences  in low ground with 2 miles of the shore.

Category 5 [Catastrophic] Trees, shrub, and all signs blown down; considerable damage to roofs of  buildings, with very severe and extensive damage to winds and doors; complete failure on many roofs of residences and industrial buildings; extensive shattering
of glass in windows and doors; complete buildings destroyed; small building overturned or blown away; mobile homes demolished major damage to lower floors of all structures less than 15 feet above sea level within 1500 feet of the shore low lying escape routes inland cut off by rising water about 3 to 5 hours before  landfall; major erosion of beaches massive evacuation of residential areas on low ground
within 5 to 10 miles of the shore may be required.
 

Note:  This scale was developed in the early 1970s by Herbert Saffir, a consulting engineer in Coral Gables, Florida, and Dr. Robert Simpson, then Director of the National Hurricane Center. The scale is based primarily on wind speeds and includes estimates of barometric pressure and storm surge associated with each of the five categories. 

[Information courtesy of Hurricanes!, Peter R. Chaston. and The Weather Channel]