Northeast monsoon arrives early over Tamil Nadu; heavy rains lash many districts

The Northeast monsoon, which accounts for the bulk of Tamil Nadu’s annual rainfall, arrived on Thursday, October 16, 2025, making an early start ahead of its normal arrival date of October 20.

The Regional Meteorological Center (RMC), Chennai, on Thursday announced the exit of the Southwest monsoon from the country and the onset of Northeast monsoon rains in parts of the southern peninsular region, including Tamil Nadu, Puducherry and Karaikal.

The onset of the upper air cyclonic circulation and easterly winds, which dominate in the Comorin region and bring quite widespread rainfall to many parts of the state, were cited as key indicators of the arrival of the Northeast monsoon.

It may be recalled that Tamil Nadu also witnessed the early onset of the Northeast monsoon on October 15 last year. Monsoon struck a positive note with 33% excess rainfall.

This year, the initial impact of the monsoon caused heavy showers in many places. Very heavy rainfall of 15 cm fell in Kayalpattinam and Thoothukudi in the 24 hours ending 8.30 am on Thursday, followed by Thiruchendur with 13 cm. Heavy rainfall was also reported in many other places, including Ranipet, Tirunelveli and Mayiladuthurai. Moderate rains affected many places in and around Chennai.

RMC has issued an orange alert for Theni, Tenkasi, Tirunelveli and Ramanathapuram districts, warning of isolated very heavy rainfall on Thursday. Heavy rain is also expected in 22 districts, including Chennai, Madurai and Erode.

Meanwhile, the Water Resources Department increased the water release from Poondi reservoir in Tiruvallur district to 4,500 cubic feet per second on Thursday due to heavy water flow. The water level in the reservoir, one of Chennai’s major sources of drinking water, has been rising steadily. Some of the water released into the Kosasthalaiyar river is diverted to the Cholavaram tank for storage, while the rest is diverted to check dams downstream, officials said.