Tropical Depression
Tropical cyclones with an organized system of clouds and thunderstorms with a defined circulation, and maximum sustained winds of 38 mph (61 kph) or less are called "tropical depressions."

Tropical Storm
Once the tropical cyclone reaches winds of at least 39 mph (63 kph) it is typically called a "tropical storm" and assigned a name.

Hurricane
Once a hurricane forms, it is rated on the Saffir-Simpson Hurricane Scale. There are five categories in this rating system.

Saffir-Simpson Hurricane Scale

Category	Wind Speed	Effects
1	74 to 95 mph (64-82 kt or 119-153 kph)	Storm surge 4 to 5 ft (1.2 to 1.5 m) above normal Some coastal road flooding Little or no structural damage
2	96 to 110 mph (83-95 kt or 155-177 kph)	Storm surge 6 to 8 ft (1.8 to 2.4 m) above normal Trees down Roof damage (shingles ripped off) Coastal and low-lying escape routes flood 2-4 hours before arrival of the hurricane center
3	111 to 130 mph (96-113 kt or 178.6-209 kph)	Storm surge 9 to 12 ft (2.7 to 3.7 m) above normal Structural damage in houses Mobile homes destroyed Severe flooding Low-lying escape routes are cut by rising water 3-5 hours before arrival of the center of the hurricane Evacuation of low-lying residences with several blocks of the shoreline
4	131 to 154 mph (114-135 kt or 210-247.8 kph)	Storm surge 13 to 18 ft (4 to 5.5 m) above normal Severe flooding inland Some roofs ripped off Major structural damage Massive evacuation of residential areas up to 6 miles inland
5	>155 mph (> 135 kt or > 249.4 kph)	Storm surge at least 18 ft (5.5 m) above normal Severe flooding further inland Serious damage to most wooden structures Massive evacuation of residential areas on low ground within 5-10 miles (8-16 km) of the shoreline