Here is your ten-point cheat sheet on this big story:
"Spoke to Tamil Nadu Chief Minister Shri Edappadi K Palaniswami and Puducherry Chief Minister Shri V Narayanasamy regarding the situation in the wake of Cyclone Nivar. Assured all possible support from the Centre. I pray for the safety and well-being of those living in the affected areas," the Prime Minister tweeted in English and Tamil.
The Puducherry Chief Minister spoke to NDTV on Tuesday and said large gatherings had been banned and public movement prohibited from 9 PM to 6 AM Thursday. He also said non-essential shops and services had been shut; only milk booths, fuel stations, hospitals and pharmacies, and government offices will be allowed to open.
The Tamil Nadu government has said that those involved in essential services will continue to work. Chief Minister Palaniswami appealed to people to stay indoors as far as possible and said over 4,000 "vulnerable" locations had been identified and local officials have been told to ensure peoples' safety.
With memories of the 2015 floods still fresh, Tamil Nadu is also monitoring four reservoirs - Poondi, Cholavaram, Red Hills and Chembarambakkam - in anticipation of a rapid rise in water levels. Revenue Minister RB Udhayakumar, who heads the state Disaster Management Department, told NDTV: "We are ensuring clear channels for smooth flow of water and safe storage in large lakes".
Puducherry has installed ''Number 7 storm warning cage at port areas'', which means the port will experience severe weather from a storm of light or moderate intensity that is expected to cross over or near the port.
Around 1,200 National Disaster Response Force personnel have been deployed in Tamil Nadu, Puducherry and neighbouring Andhra Pradesh as well, NDRF chief SN Pradhan told PTI. 12 teams are in Tamil Nadu (six in Cuddalore district and two in Chennai), seven in Andhra Pradesh and three in Puducherry. An additional 20 teams will be on standby in Odisha's Cuttack, Vijaywada in Andhra Pradesh and Thrissur in Kerala.
The Indian Navy has said it is closely monitoring the movement of Nivar, and is in constant touch with officials of both Tamil Nadu and Puducherry governments. Naval ships, aircraft and rescue and diving teams have been kept on standby.
State governments expect widespread damage to power lines and communication networks, with fears that houses in rural areas will be destroyed and trees will be uprooted. Both governments have also sounded warnings to fishing communities and relocated thousands of people from coastal and low-lying regions, which may be hit by tidal waves up to a metre in height.
An alert has been sounded at the Madras Atomic Power Station (MAPS) in Tamil Nadu's Kalpakkam, which is around 20 km from Mamallapuram. Authorities are closely monitoring the weather to take action as required, officials told news agency PTI.
Andhra Pradesh Chief Minister Jaganmohan Reddy has also sounded an alert. The state is expected to receive heavy rainfall as Nivar moves inland. Nellore and Chittoor districts are on alert, as are parts of Kadapa, Kurnool and Anantpur, with between 11 and 20 cm of rain and wind speeds of up to 75 km per hour expected. Fishermen have been advised not to go out to sea and low-lying areas have been warned of flooding.
With input from PTI
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