Tamil Nadu Weather: Fresh Spell From Jan 9 To Soak As TN Set To Get Excess Rains In Jan

Tamil Nadu, a state whose winter months are historically characterized by dry, cool weather, is preparing for yet another significant spell of unseasonal rainfall, as per weather blogger R Pradeep.

The blogger has identified a fresh Upper Air Cyclonic circulation (UAC) developing off the coast of Sri Lanka, which is poised to drench the Tamil Nadu coast and interior regions from January 9/10 through January 13/14.

This upcoming event is not an anomaly but part of a striking and persistent climatic shift. The blogger has provided an analysis of the last five years which reveals that January, traditionally Tamil Nadu's weakest rainfall month with a long-period average of a mere 12.3 mm, has consistently punched far above its weight. Barring a deficient year in 2023, the state has recorded excess to super-excess rainfall each January, regardless of broader El Niño or La Niña influences.

The data is telling: from a 139.3 mm in 2021 to 34.8 mm in 2022, 50.5 mm in 2024, and 24.3 mm in 2025. The trend shows no sign of breaking in 2026. The state has already registered 7.8 mm of rain in the first five days of the month alone, and the impending spell all but guarantees January will end yet again in the 'excess' category, the blogger said in the post.

The capital city of Chennai epitomizes this dramatic change. Once expecting a modest 16.2 mm in January, the city has seen its climate norms rewritten. Four of the last five years have ended with excess rainfall, including monumental deluges of 166.2 mm in 2021 and 90.3 mm in 2022. With 30.0 mm already recorded as of January 5 and more rain forecast, Chennai is on course for another notably wet start to the year.

He wrote, "Delta (Nagai, Tiruvarur, Mayiladuthurai, Karaikkal and Thanjavur) and Cuddalore will be in hot spot and Other parts of North Tamil Nadu, Pondicherry, Villupuraram, KTCC (Kancheepuram, Tiruvallur, Chennai and Chengalpet), Vellore Tiruvannamalai, Ranipet, Trichy, Pudukottai, Kallakuruchi, Sivaganga, Madurai, Salem, Namakkal, Ariyalur, Perambalur and other parts of South Tamil Nadu will get rains for atleast 1 or 2 day of the total 4 days, Finish the harvesting before 9th January for being on safer side. Even Kongu belt will get rains."

A broader swath of North Tamil Nadu, including the KTCC region (Kancheepuram, Tiruvallur, Chennai, Chengalpattu), Villupuram, Vellore, Tiruvannamalai, Ranipet, and several central and southern districts, are also forecast to receive rainfall for at least a day or two during the four-day period. Even the typically drier Kongu belt is likely to see showers.

Across the Palk Strait, Sri Lanka is also set to receive rainfall from the same system. Meteorologists indicate that while heavy rain is possible, a large-scale, catastrophic flooding event on the scale of previous disasters is not anticipated. However, extreme northern parts of the island, particularly the Jaffna peninsula, need to remain vigilant. The alignment of wind convergence is near-perfect over this region, raising the potential for very heavy to extremely heavy isolated downpours.

As Tamil Nadu gears up for another wet January, the recurring pattern raises critical questions for urban planning, water management, and agricultural calendars. What was once a climatic aberration is now, for the fifth time in six years, becoming the new normal for the state's winter.