Saffir-Simpson scale (săfˈər–) [key], standard scale for rating the severity of hurricanes as a measure of the damage they cause; it is based on observations of numerous North Atlantic Basin hurricanes. First developed in the late 1960s by Herbert Saffir, a structural engineer, to quantity potential damage from hurricane winds, the scale was expanded in the early 1970s by Robert Simpson, then the Director of the National Hurricane Center. In its present form there are two definitive scales: the Saffir-Simpson Hurricane Scale and the Saffir-Simpson Hurricane Damage Intensity Scale. The Saffir-Simpson Hurricane Scale rates hurricanes from category 1 through category 5 in order of increasing intensity. Each intensity category specifies the range of conditions of four criteria: barometric (central) pressure, wind speed, storm surge, and damage potential. The Saffir-Simpson Hurricane Damage Intensity Scale, in addition to the wind speed, outlines the damage potentially possible with an associated categorized hurricane.
As popularly employed, the Saffir-Simpson scale is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf in the landfall region. A category 1, or "minimal," hurricane has winds of 74–95 mph (119–153 kph), has a storm surge of 3–5 ft (1.0–1.7 m), and will cause some damage to shrubbery, trees, and unanchored mobile homes and some flooding of low-lying coastal roads. A category 2, or "moderate," hurricane has winds of 96–110 mph (154–177 kph), has a storm surge of 6–8 ft (1.8–2.6 m), and will cause considerable damage to shrubbery with some trees being blown down, extensive damage to mobile homes, and inundation by rising water of coast roads and low-lying escape routes. A category 3, or "extensive," hurricane has winds of 111–130 mph (178–209 kph); has a storm surge of 9–12 ft (2.7–3.8 m); will cause large trees to be blown down, some structural damage to small buildings, destruction of mobile homes, and flooding of sea-level coastland 8 mi (13 km) or more inland; and requires evacuation of low-lying residences near the shoreline. A category 4, or "extreme," hurricane has winds of 131–155 mph (210–249 kph), has a storm surge of 13–18 ft (3.9–5.6 m), and will cause severe damage to roofing materials, windows, and doors, complete destruction of mobile homes, flooding of low-lying areas as much as 6 mi (10 km) inland, and major damage to structures near shore due to battering by waves and floating debris. A category 5, or "catastrophic," hurricane has winds greater than 155 mph (249 kph), has a storm surge higher than 18 ft (5.6 m), and will cause complete failure of roofs on residences and industrial buildings, the overturning or sweeping away of small buildings, and major damage to structures less than 15 ft (4.6 m) above sea level within 1,500 ft (457 m) of shore. A category 5 storm requires evacution of all residential areas on low-lying ground within 5–10 mi (8–16 km) of shore.