Northeast monsoon arrives early in Tamil Nadu
The wait for Tamil Nadu’s principal rainy season is over, with the Regional Meteorological Centre (RMC) in Chennai on Thursday, October 15, 2026, declaring the onset of the Northeast monsoon. The arrival comes five days ahead of its normal date and coincides with the withdrawal of the Southwest monsoon over the State.
Issuing an orange alert for six districts, including the Nilgiris and Madurai, the RMC forecast heavy to very heavy rainfall of up to 20 cm on Friday. It cautioned that heavy rain is likely at isolated locations across several coastal and interior districts and added that wet weather is expected to persist across Tamil Nadu through October 21, with some areas receiving heavy spells.
Onset confirmed as conditions align
According to RMC officials, the declaration of onset followed the fulfilment of multiple criteria, including the establishment of northeasterly winds and fairly widespread rainfall across the State. These conditions, they said, provided a clear signature of the seasonal shift to the Northeast monsoon regime.
Forecast: Normal season overall, regional variations likely
The RMC noted that the Southwest monsoon ended with a 20% rainfall deficit in Tamil Nadu. However, the Northeast monsoon—crucial for the State’s water storage, agriculture, and urban demand—is forecast to bring normal rainfall this season.
Within that outlook, regional variations are expected. The Delta and southern parts of Tamil Nadu have reasons for optimism, with an above-normal rainfall forecast. North coastal districts are likely to receive normal rainfall, while the north interior regions could see below-normal rainfall.
Heavy rain alert and short-term outlook
In its immediate advisory, the RMC placed six districts under an orange alert for Friday, highlighting the potential for heavy to very heavy downpours of up to 20 cm in places, including the Nilgiris and Madurai. Scattered heavy rain may also occur at isolated locations in several other coastal and interior districts. The RMC expects wet weather conditions to prevail statewide until at least October 21, with intermittent heavy rain in some pockets.
Climate drivers and uncertainty: El Niño in focus
V.R. Durai, head of the Regional Weather Forecasting Centre at the RMC, said that while El Niño is anticipated to strengthen further this year, its specific impact on Tamil Nadu’s rainfall will also be shaped by other climatic factors, notably the development of weather systems over the Bay of Bengal and the tracks taken by cyclones.
“The Bay of Bengal churns out fewer cyclones and low-pressure areas during El Niño years, even though it is associated with above-normal rainfall. Strong El Niño conditions would prevail till February, after which it may begin to lose strength,” he said.
Durai cautioned that forecasts of extreme weather events cannot be made a month in advance under the current circumstances, as atmospheric conditions continue to evolve day by day. While coastal areas could face severe weather during the season, current tools cannot reliably estimate the precise magnitude of extreme rainfall far ahead of time, he said.
He added that some coastal regions, including Karaikal, Puducherry, and Nagapattinam, currently fall within a zone of uncertainty in model projections.
Early onset not a guarantee of abundant rain, say experts
Meteorologists underscored that an early onset, by itself, does not confer a significant advantage in terms of seasonal totals. Y.E.A. Raj, former Deputy Director-General of Meteorology, said that an early start—seven or eight days ahead of schedule—does not guarantee a good rainfall season.
Citing data going back to 1901, he noted that in 12 years when the Northeast monsoon set in between October 1 and 10, Tamil Nadu received above-normal rainfall in only half of those years, including 1996 and 1977. By contrast, in six years when the monsoon onset was delayed into November, including 2000 and 1992, the State ended the season with a rainfall deficit.
Government readiness and on-ground measures
As the monsoon sets in, the State government said it has completed most preparedness activities. Minister for Revenue and Disaster Management K.A. Sengottaiyan on Thursday said all precautionary measures for the Northeast monsoon had been put in place following a series of review meetings.
Speaking to reporters at Ezhilagam in Chennai, he said that nearly 98% of the preparedness works had been completed. Hospitals and medical facilities have been kept on standby, and the readiness of Amma Unavagams to provide food has been reviewed. Educational institutions designated as rehabilitation centres have also been assessed for their preparedness, he added.
In Chennai, a team of Ministers led by Minister for Public Works Aadhav Arjuna has been tasked with overseeing monsoon preparedness and rescue operations across various zones. Additionally, IAS officers have been appointed to coordinate efforts in all 15 zones of the city.
Chief Minister C. Joseph Vijay on Thursday inspected flood-mitigation and desilting works being carried out at the Captain Cotton Canal in Vyasarpadi, as well as at the confluence of the Otteri Nullah and the Buckingham Canal in the Basin Bridge area.
Outlook
With the Northeast monsoon arriving early and wet conditions forecast through October 21, authorities and residents are preparing for a sustained spell of rain. While the seasonal outlook suggests normal rainfall overall—and potentially above-normal rainfall in the Delta and southern regions—meteorologists emphasize that daily weather systems will determine the distribution and intensity of rain. The RMC’s advisories and evolving model guidance will remain central to tracking the season’s progress and anticipating any severe weather along the coast.
