The Monsoon Climate in India is dominated by the South-West & North-East Monsoons. During summer months temperature rises along the vast Indian Ocean. The Indian Ocean, Bay of Bengal and Arabian Sea on one hand and the Indian sub-continent with the Himalaya wall on the other hand form the basis of the Monsoons. Tropic of Cancer is passing through the centre of India. Therefore, the sun’s rays fall vertical on it on the 21st June.
During this time the temperature becomes very high near the Tropic of Cancer. As a result a low pressure belt is created here in summer. But high pressure exists in the Bay of Bengal, in the Arabian Sea and in the Indian Ocean. So the wind from the high pressure belt rushes towards the low pressure belt over the seas. It becomes moisture laden at the time of blowing over the sea for long distance. As it crosses the equator it deflects to the right and blows from South-West direction. That is why it is known as the South-West Monsoon. The wind divides into two branches (i) Arabian Sea branch, (ii) Bay of Bengal branch. The Arabian Sea branch causes heavy orographic rain on the Western slopes of the Western Ghat Mountains.
After crossing the Western Ghats it enters the Deccan plateau. The Deccan plateau receives scanty rainfall and becomes a rain shadow region. It passes on towards the north and central India and there the rainfall occurs. A small part blows straight to the Aravallis. Because of its parallel situation western part of the Aravallis does not receive rainfall. Southern part of the Aravallis receives orographic rainfall.
The Bay of Bengal branch enters Bangladesh, West Bengal and Orissa. The wind goes to the north and north-east up to the foothills of Himalaya and Meghalaya plateau. Heavy rainfall occurs in the Meghalaya plateau. Mawsynram, a place near Cherrapunjee, receives the highest recorded rainfall in the world.
From there the wind turns to the left and passes over the plains of Northern India. The rainfall gradually decreases to the West. In Punjab the rainfall is very poor and uncertain. The Arabian Sea branch of the Monsoon also passes out this region but rainfall is very low here. Rainfall lasts from June to September.
In winter, the conditions are reverse. Then there is high pressure over the Indian landmass and low pressure exists over the surrounding. So the wind blows from Northern part to Southern part seas and it blow from North East. Therefore, it is known as North-East Monsoon. The wind is of land origin. So it is moisture-less, so there is little rainfall in winter in India except the Coromondal coast which receives heavy rainfall.