The Northeast monsoon, which brings a major share of Tamil Nadu’s annual rainfall, arrived on Thursday (October 16, 2025), marking an early onset ahead of its usual arrival date of October 20.
The Regional Meteorological Centre (RMC), Chennai, declared the simultaneous exit of the Southwest monsoon from the country and the onset of the Northeast monsoon rainfall over parts of the southern peninsular region, including Tamil Nadu, Puducherry, and Karaikal, on Thursday.
The upper air cyclonic circulation prevailing over Comorin area, which brought fairly widespread rainfall over many parts of the State, along with the setting in of easterly winds, were cited as key indicators for the arrival of the Northeast monsoon.
It may be recalled that Tamil Nadu also witnessed an early onset of the Northeast monsoon last year, on October 15. The monsoon signed off on a positive note with 33% excess rainfall.
This year, the monsoon’s first spell brought intense downpours in many places. In the 24 hours ending 8.30 a.m. on Thursday, Kayalpattinam and Thoothukudi received very heavy rainfall of 15 cm each, followed by Thiruchendur with 13 cm. Several other places, including Ranipet, Tirunelveli, and Mayiladuthurai also reported heavy rainfall. Moderate showers lashed many places in and around Chennai.
The RMC has issued an orange alert for Theni, Tenkasi, Tirunelveli, and Ramanathapuram districts, warning of isolated very heavy rainfall on Thursday. It has also forecast heavy rain in 22 other districts, including Chennai, Madurai, and Erode.
Meanwhile, the Water Resources Department has increased water release from the Poondi reservoir in Tiruvallur district to 4,500 cubic feet per second on Thursday due to heavy inflows. The water level in the reservoir, one of the Chennai’s key drinking water sources, is rising steadily. Officials said a portion of water released into Kosasthalaiyar river is diverted to Cholavaram tank for storage, while the rest is channelled to checkdams downstream across the river.