The Monsoon or rainy season begins from mid - June and lasts till the end of September. By the end of May, pressure over North India becomes lower due to the increasing temperature. This causes air from high-pressure zones over the Indian Ocean to move towards India as monsoon winds. These winds are moisture-laden and cause heavy rainfall in India. Since these winds, called the advancing monsoon, enter India from the southwest, they are called the south-west monsoon. During this time of the year, the southwest monsoon winds start blowing from the sea to land. When these winds strike the mountain barriers, rainfall occurs.