Rare January system over Bay of Bengal set to bring heavy rainfall to parts of T.N.

The dry spell over the State may ease as the deep depression over the Bay of Bengal is likely to bring scattered rainfall, particularly over coastal Tamil Nadu, for three days from Friday (January 9, 2026). The Bay of Bengal has witnessed only 20 intense weather systems during January since 1891, making such events unusual during this time of the year.

According to the Regional Meteorological Centre (RMC), the deep depression lies over southwest Bay of Bengal and adjoining east Equatorial Ocean, about 810 km southeast of Karaikal and 980 km south-southeast of Chennai. It is likely to cross the Sri Lanka coast between Hambantota and Kalmunai on Friday evening/night.

B. Amudha, Head (Additional in-charge), RMC, said while this is not the first time that the Bay has churned out intense weather systems during January, such events are not frequent. The deep depression is likely to bring heavy rainfall to some parts as it moves along south-coastal Tamil Nadu.

The RMC has issued orange and yellow weather alerts, indicating the possibility of intense downpour up to 20 cm in some districts. On Friday, the downpour would be restricted to delta districts and south-coastal Tamil Nadu. While Tiruvarur and Nagapattinam may receive heavy to very heavy rainfall, Ramanathapuram, Pudukottai, Mayiladuthurai, and Thanjavur are likely to receive heavy rainfall.

On Saturday (January 10), many coastal districts and some interior places may get rainfall, and it may be intense over the stretch between Chengalpattu and Ramanathapuram. While four districts, including Cuddalore and Tiruvarur, may receive heavy to very heavy rainfall, heavy rainfall may occur in isolated places in seven districts, including Pudukottai, Chengalpattu, and Ariyalur.

Why is this a rare event?

Y.E.A. Raj, former deputy director general of meteorology, Chennai, noted the prevailing system, expected to cross the Sri Lanka coast, is analogous to the January 2023 depression that crossed the island nation’s east coast.

Eleven intense weather systems formed over the Bay of Bengal between 1961 and 2024, and most of them were short-lived. None of the weather systems crossed the Tamil Nadu coast. Only two January systems in 1967 and 2005 intensified into cyclonic storms, he added.

Meanwhile, the RMC has forecast that ground frost is likely to occur over the higher ranges of the Nilgiris and Kodaikanal hills on Friday.