Jet streams are winds that blow horizontally from west to east at a high speed near the tropopause and the stratosphere. These are high speed winds which influence the weather and climatic conditions of the region over which they blow.There are two types of jet streams that blow at the tropical belt of 300 north latitudes- the westerly jet stream and the easterly jet stream.A branch of westerly jet stream brings moderate to heavy rainfall followed by the cold waves to the Indian subcontinent.The easterly jet stream also helps the Monsoon winds to blow into the greater part of India and brings monsoon showers.
Jet streams are the fast moving winds found above higher altitude.

A jet stream is a band of fast-moving wind that is high up in the atmosphere. Jet streams form at the boundaries between hot and cold air masses and tend to be westerly, which means they blow from the west to the east.