West Bengal comprises of two distinct pockets, Gangetic West Bengal and Sub Himalayan West Bengal. The weather conditions vary in both the districts. Sub Himalayan West Bengal is the region which is adjacent to hills and Gangetic West Bengal is in close vicinity of the sea.
In the pre-Monsoon season, regions of Sub Himalayan West Bengal such as Darjeeling, Cooch Behar, Siliguri and Jalpaiguri record 300 mm to 400 mm rains in the month of May. Whereas, regions in Gangetic West Bengal such as Kolkata, Midnapore, Burdwan, Malda and Digha witness rain less than or around 100 mm of rains but it does not cross 150 mm of rains in the month of May.