 Scientists also cite other factors in the formation of monsoons, including the barrier of the Himalayas on the northern fringe of the South Asia and the sun's northward tilt, which shifts the jet stream north.These factors set off a rush of moisture-rich air from the Indian Ocean over the South Asia, resulting in the southwest monsoon.The hot air that rises over the South Asia during April and May creates low-pressure areas into which the cooler, moisture-bearing winds from the Indian Ocean flow.