"Extremely heavy rainfall over Assam and Meghalaya, Sub-Himalayan West Bengal and Arunachal Pradesh during next five days" is expected, the IMD warned on Tuesday. Nagaland, Mizoram, Manipur, and Tripura will also witness heavy downpour between 15 to 18 June, the press release further said. The Regional Meteorological Centre in Guwahati issued a 'Red Alert' for Assam and Meghalaya.