More than 16,000 people in Tamil Nadu and Andhra Pradesh have been evacuated as the cyclone is likely to have a major impact respectively in the northern and southern parts of the states.
The Army, Navy and Air Force besides National Disaster Response Force personnel are on stand by for rescue and relief operations.
The Met office said Cyclone Vardah hit land with wind speeds of between 120 and 130 kmph around 2 30 pm and the rain will continue till about 6 pm.
30 diving teams with additional relief material are also on the ready.
Almost 50 flights were delayed or diverted to and from Chennai this morning and suburban train services have been suspended.
All schools and colleges are closed in Chennai, Kancheepuram and Tiruvallur, besides coastal areas of Villupuram.
The Tamil Nadu Government has also asked private offices to allow their staff to take a day off or work from home.
The Met department said the sea will be rough along and off the Andhra Pradesh and north Tamil Nadu coasts for the next two days. Fishermen have been asked to avoid going out to sea in this period.
174 relief centres are ready to receive evacuated people in Chennai.