The jet stream is a band of swiftly moving air located high in the atmosphere and affects the movement of storms and air masses closer to the ground. The currents of air flow from west to east and are usually a few miles deep, up to 100 miles (160 kilometers) wide, and well over 1,000 miles (1,600 kilometers) in length. The speed at which the air travels in the jet stream is over 57.5 miles (92 kilometers) per hour, sometimes moving as fast as 230 miles (386 kilometers) per hour.

There are two polar jet streams, one in each hemisphere. The jet streams meander across the troposphere and stratosphere (up to 30 miles [48 kilometers] high) and between 30 and 70 degrees latitude. There are also two subtropical jet streams (one in each hemisphere) that range between 20 and 50 degrees latitude. The subtropical streams flow between altitudes of 30,000 to 45,000 feet (9,150 to 13,700 meters) and are even swifter than the polar streams, moving at speeds of over 345 miles (550 kilometers) per hour.