General Hurricane Information

What is a Hurricane?

A hurricane is a type of tropical cyclone: a powerful, organized storm system that forms over warm ocean waters in the tropics. It is characterized by:

• Sustained winds of at least 74 mph (119 km/h)
  
• A low-pressure center (called the “eye”) surrounded by a rotating system of thunderstorms
  
• Heavy rainfall, strong winds, and often storm surges along coastlines

How They Form:

1. Warm ocean water (at least 80°F or 27°C) provides energy.
   
2. Moist air rises from the ocean surface, cools, and forms clouds.
   
3. As the system organizes, Earth's rotation causes it to spin (Coriolis effect).
   
4. If conditions are right (low wind shear, moist environment), the system strengthens into a hurricane.

Naming and Categories:

• In the Atlantic and Northeast Pacific, these storms are called hurricanes.
  
• In the Northwest Pacific, they are called typhoons.
  
• In the South Pacific and Indian Ocean, they’re often called cyclones.

Hurricane Classification 

Hurricanes are classified on the Saffir-Simpson Hurricane Wind Scale (Category 1–5) based on their sustained wind speed. Category 5 is the most intense, with winds exceeding 157 mph (252 km/h).

To learn more about current tropical conditions visit the National Hurricane Center.

National Hurricane Center

Page last updated 4:48 PM, July 18, 2025