A tropical cyclone officially becomes a hurricane when its winds exceed 64 knots (74 mph). In the United States, storm strength is classified as follows:

• Tropical Disturbance: A low-pressure area of disturbed weather.
• Tropical Depression: A low-pressure area with a cyclonic circulation and sustained winds less than 34 knot (39 mph).
• Tropical Storm: A cyclone with sustained winds greater than 34 knots (39 mph), but less than 64 knots (74 mph). The system is named at this time.
• Hurricane: A cyclone with sustained winds exceeding 64 knots (74 mph). Hurricanes are categorized by the Saffir-Simpson Scale.