Tamil Nadu braces for more heavy rain as fresh Bay of Bengal system forms
The northeast monsoon has become vigorous over Tamil Nadu, bringing heavy overnight rain to several parts of the State. A fresh weather system is taking shape over the Bay of Bengal, and the Regional Meteorological Centre (RMC) expects widespread rain to continue, especially in southern and delta districts, over the next few days.
A low-pressure area is forecast to form over the southwest Bay of Bengal, off the Tamil Nadu coast, in the early hours of Wednesday (October 21, 2026). Back-to-back weather systems over the Bay are expected to keep rainfall intense across the State this week. The wet spell is likely to last till October 27, according to officials.
Several areas in and around Chennai received heavy overnight rain. MGR Nagar recorded 15 cm in the 24-hour period ending 8.30 a.m. on Wednesday, the highest in the city, while Vadapalani recorded 14 cm. The rain also brought considerable inflow into Chennai’s major drinking water reservoirs.
The Central Water Commission has warned of a possible rise in water levels in the Vaigai, Tamirabharani, Bhavani, Noyyal, Aliyar and Moyar rivers in districts including Coimbatore and Theni till Friday. An above-normal flood situation is expected in the Kodaiyar in Kanniyakumari district and the Paralayar in Tenkasi district. Major reservoirs such as Manimuthar and Pechiparai may also receive increased inflow.
The RMC is monitoring the prospects of another system developing over the Bay of Bengal on October 23. V.R. Durai, head of the Regional Weather Forecasting Centre at the RMC, said the agency was watching the intensity and movement of the developing system. While it could move northwestwards and strengthen into a depression, weather models indicated that it may not have much impact on Tamil Nadu, he said. October systems forming over the Bay of Bengal usually tend to move towards Andhra Pradesh, Mr. Durai added.
On Thursday, isolated places in 17 southern, Western Ghats and delta districts, including the Nilgiris, Tenkasi, Nagapattinam and Madurai, may receive very heavy rainfall of up to 20 cm. Nine other districts, including Erode, Namakkal and Cuddalore, may record heavy rainfall. A similar pattern may continue till October 26. Rainfall intensity may ease over Chennai and nearby districts for a few days and pick up pace on October 25.
The RMC had issued a red alert for Chennai on Sunday and downgraded it later. Mr. Durai said such warnings are issued to help administrative preparedness when exceptionally heavy rainfall has occurred and very heavy rainfall is forecast for the following day. The alert was downgraded as the weather system weakened. The technical team of the Greater Chennai Corporation has been advised to examine the city’s weather observation network for discrepancies in rainfall data, he said.
The northeast monsoon, which runs from October to December, is a key source of water for Tamil Nadu, but intense spells can cause flooding and disrupt daily life. Officials are tracking river levels and reservoir inflows, while the weather agency continues to monitor the Bay of Bengal systems. The RMC’s forecasts and local authority advisories remain the key guide for residents in affected districts.
