Officials in the Regional Meteorological Centre of Assam said several places in Mizoram, Tripura, Meghalaya and Barak valley of Assam had been witnessing heavy rainfall since last night.
The wind speed in parts of south Assam and Meghalaya was over 40 kmph.
Updated at 1200 hrs: Over 50 people were killed and hundreds were missing in Bangladesh as one of the worst cyclones in decades ravaged its southwestern coast, destroying homes, uprooting trees and snapping power lines.
At least 300 trawlers with over 1,000 fishermen were reported missing as cyclone Sidr, packing winds up to 240 km, battered the coastline after it made landfall at the Khulna-Barisal coast last evening and swept central Bangladesh including capital Dhaka.
The worst-hit were the Sundarban forests and Khulna and Barisal districts as the cyclone started from northern Bay of Bengal with tidal surges of over 10ft inundating large areas.
Home Ministry officials said at least 50 people were killed and the death toll was likely to rise.
Over six lakh people, especially those living in coastal zone, were evacuated in the last two days.