Coastal districts of Tamil Nadu and Andhra Pradesh braced for a cyclonic storm that is expected to make landfall tomorrow, as incessant rains hit normal life today in Chennai.

Authorities were put on high alert after a deep depression lying 500 km south east of Chennai intensified into a cyclonic storm and is expected to cross the coast between Nagapattinam in Tamil Nadu and Nellore in Andhra Pradesh tomorrow, bringing in torrential rains in the region.

The system, named 'Nilam', as suggested by Pakistan under the cyclone naming procedure, would move northwestwards and cross the coast between Nagapattinam and Nellore by tomorrow afternoon/evening.

Under the influence of the storm, rainfall at most places, with isolated heavy to very heavy rainfall, would occur over coastal Tamil Nadu and Puducherry during next 12 hours, a bulletin issued by Area Cyclone Warning Centre here at 1 pm said.

It forecast heavy to very heavy rainfall and isolated extremely heavy rainfall (25 cm or more) in the region during the subsequent 36 hours.

"Squally winds speed reaching 45-55 kmph gusting to 65 kmph would prevail along and off north Tamil Nadu, Puducherry and adjoining south Andhra Pradesh coasts during next 12 hours. The wind speed would gradually increase thereafter as the system comes closer to coast," it said.

Sea will be "very rough to high" and fishermen in Tamil Nadu, Puducherry and adjoining south Andhra Pradesh coasts have been advised to stay off the sea.

Windspeeds can reach upto 90 km in Chennai and there could be some disruption in communication lines, the bulletin said.

Danger signals ranging from five to seven have been hoisted at Chennai, Ennore, Cuddalore, Nagapattinam and Puducherry ports.

Normal life in Chennai, Kancheepuram, Cuddalore and Villupuram was hit by incessant rains since morning. A holiday was declared today for schools and colleges.

In AP, a third warning signal has been issued in Krishnapatnam, Vadarevu, Machilipatnam and Nizampatnam ports while fishermen have been warned not to venture into sea.

Control rooms have been opened in the coastal districts, particularly SPS Nellore and Prakasam that are expected to face a major impact of the cyclone.