Jet streams are high-velocity westerly winds blowing through a narrow zone, around 12,000 meters over the troposphere. These are actually, westerly winds blowing at higher altitude. Their velocity (speed) recorded in summer is about 110 km/h and about 184 km/h. in winter. These blow at the mid-latitude and over sub-tropical regions (north half of India).

These streams are located over 27-30° north latitude. The westerly flows are responsible for western disturbances and the easterly flows cause tropical depressions during monsoon and even in early winter season.