Hurricanes are high-speed windstorms that start over the ocean and can have winds as fast as 250 kilometres per hour. Hurricanes usually happen over oceans, near the equator. They are formed when warm, wet air is forced upward by heavier, cool air. The air pressure drops quickly from the outer edge towards the centre. This causes the wind speed to rise. The winds move in a circular pattern around the centre, "eye", of the hurricane. In the "eye", the winds stop and the clouds lift, but the ocean below remains violent. The average hurricane covers an area of at least 240 kilometres. When the storm is over land, these winds destroy life and property.