How do hurricanes form?

Warm ocean waters and thunderstorms fuel power-hungry hurricanes.

satellite image of Hurricane Katrina

Hurricanes form over the ocean, often beginning as a tropical wave—a low pressure area that moves through the moisture-rich tropics, possibly enhancing shower and thunderstorm activity.

Recipe for a Hurricane

Whipping up a hurricane calls for a number of ingredients readily available in tropical areas:

  • A pre-existing weather disturbance: A hurricane often starts out as a tropical wave.

  • Warm water: Water at least 26.5 degrees Celsius over a depth of 50 meters powers the storm.

  • Thunderstorm activity: Thunderstorms turn ocean heat into hurricane fuel.

  • Low wind shear: A large difference in wind speed and direction around or near the storm can weaken it.

Mix it all together, and you’ve got a hurricane—maybe. Even when all these factors come together, a hurricane doesn’t always develop.

Hurricanes are powerhouse weather events that suck heat from tropical waters to fuel their fury. These violent storms form over the ocean, often beginning as a tropical wave—a low pressure area that moves through the moisture-rich tropics, possibly enhancing shower and thunderstorm activity.

As this weather system moves westward across the tropics, warm ocean air rises into the storm, forming an area of low pressure underneath. This causes more air to rush in. The air then rises and cools, forming clouds and thunderstorms. Up in the clouds, water condenses and forms droplets, releasing even more heat to power the storm.

When wind speeds within such a storm reach 74 mph, it’s classified as a hurricane. The terms “hurricane” and “tropical cyclone” refer to the same kind of storm: a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, low-level circulation.

During just one hurricane, raging winds can churn out about half as much energy as the electrical generating capacity of the entire world, while cloud and rain formation from the same storm might release a staggering 400 times that amount.