At about what wind speed does a tropical storm become a hurricane?

A hurricane is a kind of storm called a tropical cyclone. It forms over warm tropical or subtropical waters, spins around an area of low pressure, and carries organised bands of thunderstorms.

Scientists sort tropical cyclones by the speed of their strongest steady winds. A storm with winds below about 63 km an hour is called a tropical depression. Once its winds reach about 63 km an hour, it becomes a tropical storm. And when they reach about 119 km an hour, it is called a hurricane.

Hurricanes themselves are rated from category 1 to category 5 on the Saffir-Simpson scale, according to their winds. The higher the category, the more damage a storm can do to buildings and property.

The name "hurricane" is used for such storms that form in the Atlantic Ocean, the Caribbean Sea and parts of the Pacific. Each one is given a name from a list kept by the World Meteorological Organization, which makes it easier to warn people and to talk about more than one storm at a time.

In the Atlantic, the hurricane season runs from 1 June to 30 November, although storms can and do form outside those months.