Tamil Nadu’s 2026 northeast monsoon is expected to deliver near-normal rainfall overall, but an El Nino-linked pattern could produce prolonged rain in coastal districts while leaving interior areas comparatively dry, according to a forecast by Tamil Nadu Agricultural University’s Agro Climate Research Centre.
The centre’s district-level forecast covers the northeast monsoon period from October to December. It estimates that Tamil Nadu could receive 468 mm of rainfall during the season, broadly matching the long-term average of 464 mm. The forecast comes after the state recorded 254 mm of rain between June 1 and September 22, which was 13 per cent below its long-term average of 292 mm for the period.
The expected near-normal northeast monsoon could partly offset the earlier shortfall, the report said. Improved rainfall during the season may raise water levels in reservoirs and other water bodies and support groundwater recharge. However, the distribution of rain is expected to be uneven, making the location and intensity of rainfall as important as the statewide total.
The centre said the prevailing El Nino event could lead to differences in the spread of the monsoon. Coastal districts may receive repeated heavy rain associated with cyclonic systems, while interior districts could experience continuing dry conditions. The forecast does not indicate that all districts will receive the expected rainfall evenly.
The northeast monsoon is particularly important for Tamil Nadu because it contributes about half of the state’s annual rainfall. The season therefore has direct implications for agriculture and water management. The centre advised farmers to store excess rainwater in farm ponds when heavier rainfall occurs so that it can be used for irrigation during later dry periods.
The forecast also places attention on the state’s uneven water geography. Rainfall in the coastal belt may create short periods of surplus water, while districts away from the coast may continue to face limited replenishment if dry spells persist. For local administrations and water managers, this means that statewide rainfall projections may not fully reflect conditions in individual districts.
Sathyamurthy, head of the Agricultural Climate Research Centre, said the forecast covered rainfall expected over the next three months. He said the northeast monsoon was likely to begin in the second week of October and become fully established by the third week of the month.
Sathyamurthy also said rain was being recorded in the Western Ghats around Coimbatore, including the areas around Kovai Courtallam and the Siruvani dam. The centre’s forecast places the coming monsoon within a range close to Tamil Nadu’s usual northeast monsoon rainfall, but the district-level variation linked to the prevailing weather pattern remains the key operational concern for agriculture and water storage.
