Jet streams are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter. A number of jet streams exist but the most constant are the mid-latitude and the sub-tropical jet stream. The jet streams located over 27°-30° north latitudes are known as subtropical westerly jet streams. These jet streams blow south of the Himalayas throughout the year except in summer. These are responsible for the western cyclonic disturbances experienced in the north and north western parts of the country. These jet streams move north of the Himalayas with the apparent migration of the sun.

During the summers at about 14°N, an easterly jet stream called the subtropical easterly jet stream blows over peninsular India.