A cyclone is a low-pressure area. In a cyclone, winds rotate in a spiral Cyclones can be big enough to cover one-half of the United States. Cyclones all share two characteristics: (a) the atmospheric pressure in the center is the lowest, and (b) the winds usually spiral inward. However, if you are in the Northern Hemisphere, the winds spiral in a counterclockwise direction. If you are in the Southern Hemisphere, the winds spiral in a clockwise direction. Storms usually occur with cyclones but not always. A cyclone can occur when the air pressure is low.

A cyclone can form in different kinds of air. If it's formed in dry air, there may not even be any clouds. Cyclones can be warm or cold in the center. A very intense cyclone is known as a tornado. A tropical cyclone is formed over warm waters in the ocean. If it's formed over the West Indies or the Eastern Pacific, it's called a hurricane. If it's formed over the Western Pacific, it's called a typhoon.