Unexpected heavy rain began lashing the area last Thursday, nearly two weeks ahead of the monsoon season, which usually occurs in the country from early July to September.
So far, at least 35 people have been killed and some 800 villages have been flooded. Over 350,000 people from the flooded villages have taken shelter in camps set up by the Indian government. Troops have been deployed in the worst-hit areas.
Weather forecasters predict more rain in the next 24 hours in West Bengal and Orissa.