Jet streams, which are rapidly moving ribbons of air 6 to 9 miles above the Earth, influence the weather by separating warm and cold air and pushing weather systems around the globe. The movement of a jet stream affects temperatures and precipitation. Meteorologists describe jet streams as resembling rivers in their flow.
The average jet stream is a band of wind traveling between 120 and 250 miles per hour. Each jet stream is up to several hundred miles wide and thousands of miles long.
Each winter, the polar jet stream moves south and grows stronger as the North Pole grows colder. Each winter, the polar jet stream reaches the United States, influencing weather in much of the country.
Those hiking Mount Everest, the world's tallest mountain, sometimes encounter the jet stream in the form of powerful, icy winds. These winds are sometimes so high and cold that they are forced to remain in their tents until they subside.
The subtropical jet stream near the southeastern portion of the U.S. also moves and shifts throughout the year. It tends to have the most dramatic impact when there is an El Niño weather event in effect. During these times, it creates wetter and colder conditions in Florida and Georgia in particular.