Excerpt From: Aerial Superhighway | Wikimedia Commons
Jet streams are narrow bands of strong winds high in the atmosphere that blow from west to east around the Earth. The Polar Jet in each hemisphere is in the region of 50°-60° latitude and the Subtropical Jet is found ~30°latitude. Jet streams can vary in height and can have speeds up to 275 mph! The fastest winds in the jet stream are known as a jet streak.