A low is expected over the southeast Bay of Bengal around 12 or 13 November, and Chennai forecasters say it could strengthen, possibly into a cyclone.
Nobody at the Regional Meteorological Centre (RMC) in Chennai is calling it a cyclone yet. The system the centre has watched for a week should now take shape as a low pressure area over the southeast Bay of Bengal around 12 or 13 November and become a well-marked low within the following 24 hours. Weather officials said on Tuesday it could intensify into a cyclonic storm next week. In the same breath they cautioned that its formation, strength, track and landfall all remain uncertain. One early assessment had the system heading towards Sri Lanka by 15 November and, if it gains strength, reaching the Tamil Nadu coast around 19 November or later.
That is a shift in tone.
IMD’s extended range outlook of 5 November gave only a low probability of the system becoming even a depression, over the southwest Bay around 15 November. It expected below-normal rain over most of the State for 6 to 12 November.
The delta and the south get the rain first
For Chennai, Wednesday looks like a day of light showers with thunder and lightning in parts of the city. The RMC put the maximum at around 33°C and the minimum at around 25°C. The heavier falls stay south: IMD’s district forecast of 9 November had heavy rain at isolated places in Ramanathapuram and Thoothukudi on 10 November, and moderate rain in the delta and southern districts, including Tirunelveli and Kanyakumari, on 11 and 12 November.
North coastal districts follow. The same forecast has light rain at isolated places in Chennai and its neighbouring districts on 13 November, then heavy rain at isolated places in Thanjavur, Thiruvarur, Mayiladuthurai, Nagapattinam and Karaikal on 15 November. Officials expect rain somewhere in the State until the 15th. Another substantial spell is possible between 15 and 20 November as the system nears the coast.
Statewide the season is 4% ahead; Chennai district is behind
Tamil Nadu and Puducherry have had 258.8 mm since 1 October against a normal of 249.8 mm, IMD’s seasonal tally to 10 November shows. A surplus of 4%. The district columns split sharply. Coimbatore leads the State with a 56% surplus, while Thanjavur, the same delta district now on the 15 November heavy-rain list, sits at minus 47%, the worst anywhere in Tamil Nadu. Around the capital the picture is mixed: Tiruvallur is 6% above normal, Kancheepuram 23% short and Chengalpattu 37% short, which means a district of Chengalpattu’s size has missed more than a third of its usual October and early November rain.
| Area | Actual (mm) | Normal (mm) | Departure |
|---|---|---|---|
| Tamil Nadu and Puducherry | 258.8 | 249.8 | +4% |
| Chennai district | 389.0 | 413.9 | -6% |
| Tiruvallur | 338.8 | 319.1 | +6% |
| Kancheepuram | 225.7 | 294.0 | -23% |
| Chengalpattu | 223.0 | 352.6 | -37% |
Source: IMD Regional Meteorological Centre Chennai, seasonal rainfall 1 October to 10 November 2026.
Chennai district stands at 389.0 mm against a normal of 413.9 mm. The Nungambakkam observatory, a single station, reads far wetter: the RMC’s 9 November report logged 608.3 mm there since 1 October, 175.1 mm above normal.
No warning was in force for any Tamil Nadu port in the RMC bulletin issued at 10 am on 10 November.
How we worked this out
Seasonal figures are IMD’s district-wise cumulative rainfall for 1 October to 10 November 2026, published by RMC Chennai, with departures as IMD gives them. The Nungambakkam figure is from the RMC daily weather report of 9 November. District totals average several rain gauges, so they do not match a single station. Forecast details come from the RMC’s district forecast and extended range outlook; the cyclone assessment was given by weather officials on 10 November and is not an IMD warning.
Checked against official sources on 11 November 2026.
Sources
- Daily Weather Report, Tamil Nadu, Puducherry and Karaikal, Regional Meteorological Centre Chennai (IMD), 9 November 2026
- District-wise seasonal rainfall, 1 October to 10 November 2026, Regional Meteorological Centre Chennai (IMD)
- Extended Range Forecast, Regional Meteorological Centre Chennai (IMD), 5 November 2026
- Port Warning bulletin, Regional Meteorological Centre Chennai (IMD), 10 November 2026
