Heavy downpour since Wednesday night has paralysed normal life in Chennai and its suburbs.
Most international flights scheduled to arrive at the city airport have been diverted to the Thiruvananthapuram airport, sources said, adding that departures are also likely to be delayed.
Four flights, three of them international, have been diverted to Bangalore after heavy rainfall flooded the runway at the Anna International Airport.
Airport sources said Mumbai-Chennai Air India flight, Dubai-Chennai Emirates Airlines flight, Muscat-Chennai Oman Airlines flight and Colombo-Chennai Sahara Airlines flight were diverted to Bangalore.
These flights were scheduled to land in Chennai between 03:30 AM and 06:00 AM.
Union Minister of State for Home S Regupathy was among the passengers on the Mumbai-Chennai flight.
However, operations remained unaffected except for minor delays at the Kamaraj Domestic Airport.
Meanwhile, several areas in Chennai are under knee-deep water while low-lying areas in north Chennai are inundated as the city recorded 20 cm of rain.
Over 4,000 people have been evacuated and lodged in 250 corporation-run schools in various parts of the city, corporation officials said on Thursday.
The government has declared a holiday for schools and colleges in Chennai, and in Tiruvallur and Kanchipuram districts where more rains have been forecast due to a depression in the Bay of Bengal.
The Southern Railway has cancelled all trains leaving Chennai Central station till 1200 noon Friday.
The decision was taken as tracks were flooded at several places, a railway release said in Chennai.
Meanwhile, railway sources said nearly 10 counters had been opened to reimburse those passengers who were planning to travel on Thursday and Friday.
Rain water has also submerged tracks between Mamballam and Egmore stations in the suburban Tambaram-Chennai beach section.
Authorities are maintaining skeletal bus services even as most auto-rickshaws remained off the roads. Most of the roads and subways are under water.
A report from Pondicherry said various parts of the Union Territory too have been experiencing non-stop rains since Wednesday night, affecting normal life.
The territorial administration has declared a holiday for all educational institutions, including private ones, on Thursday in view of the incessant rains.
Meanwhile, the depression over the southwest Bay of Bengal has moved closer towards coastal region and now threatens to bring fresh spell of heavy rains in the neighbouring state of Andhra Pradesh, which has been ravaged by floods in the past few days.
The depression was about 500 km Southeast of Machilipatnam on Wednesday evening and was likely to intensify further and move in northwesterly direction.
As a result, heavy rainfall was likely at many places of Andhra Pradesh during the next 48 hours, a bulletin issued by cyclone warning centre in Visakhapatnam said.
Floods in two spells have already claimed more than 100 lives and destroyed property worth more than Rs 2,600 crore.