The rainfall decreases from east to west in the Northern plain while it increases in the Peninsular India due to the following reasons:
- Northern plains receive rains by South West Monsoons. These Monsoons being the branch of Bay of Bengal Monsoon move westwards along the Himalayas.
- These monsoon winds on moving away to western part of country gradually loose moisture causing less rainfall. Hence rainfall decreases from east to west.
- In the Peninsular India, the rain is received by the Arabian Sea branch of South West Monsoons. The South West Monsoon winds cause heavy rainfall on the western slopes of Western Ghats as they pass through the rain bearing area of the region.
- The moment, these winds cross the Western Ghats towards east, they become dry owing to the rain shadow area and therefore rainfall starts decreasing.