In India, the rainfall is brought by the southwest monsoon winds.
As they approach the sub-continent, they split into 2 branches- namely Arabian sea branch and Bay of Bengal branch.
The Arabian sea branch sheds a lot of rainfall at the northeastern part of India as the presence of Garo, Khasi and Jaintia hills wind them up over there. Whereas, in the northwestern part, as it lies in the rain shadow region of Aravallis, they receive little to no rainfall. This is an example for the vast difference in distribution of rainfall in India.
One main reason for the uneven distribution of rainfall in India is the varied terrain and landscape.