Because hurricanes use warm, moist air as fuel, they form over warm ocean waters near the equator. According to NASA, a hurricane is a type of tropical cyclone that forms over the surface of the Atlantic or eastern Pacific Ocean.
The warm air rises above the ocean's surface, and surrounding air rushes into the low pressure area that is left behind by the warm air. The new air in the low pressure area also becomes warm and moist, rising and motivating the swirling wind pattern. The warmed air cools as it rises, and the evaporated water vapor forms clouds. When the swirling winds reach a speed of 39 mph, the storm is called a "tropical storm." At 74 mph, the storm is officially a hurricane.