A red alert has been issued for Theni, Dindigul, and Madurai districts of Tamil Nadu on Sunday, 26 October 2025, with the Regional Meteorological Centre (RMC) forecasting extremely heavy rainfall at isolated locations as the northeast monsoon continues to strengthen across the state. The three districts could receive more than 20 centimetres of rain at one or two locations, accompanied by thunderstorms, lightning, and strong winds.

Districts Under Red and Orange Alerts

The red alert — the most severe weather warning category — places Theni, Dindigul, and Madurai under maximum scrutiny for Sunday. An orange alert has been simultaneously issued for Cuddalore, Mayiladuthurai, Nagapattinam, Tiruvarur, Thanjavur, Pudukkottai, Ariyalur, Perambalur, Tiruchi, Karur, the Nilgiris, Coimbatore, Tiruppur, and Sivaganga, as well as the Karaikal region. These areas are expected to experience heavy to very heavy rainfall with thunder and lightning.

The alerts collectively cover southern, central, delta, and western parts of Tamil Nadu, indicating that the intensity of rainfall is likely to vary significantly across the affected regions.

Nilgiris Records Extremely Heavy Rain

According to the weather department, the Nilgiris recorded exceptionally heavy rainfall during the 24 hours ending at 8:30 am on Saturday. Burliar logged the highest accumulation at 25 centimetres, followed by Lower Kotagiri Estate with 20 centimetres and Coonoor with 17 centimetres. The hill district's rainfall figures add to concerns over the continuing monsoon spell, with further heavy rain forecast for the Nilgiris under the current orange alert.

Bay of Bengal System Strengthening Into Cyclonic Storm

The warnings come as a weather system over the Bay of Bengal rapidly intensifies. A low-pressure area over the east-central and adjoining southeast Bay of Bengal intensified into a well-marked low-pressure area on Saturday before developing into a depression, according to the department. The system is expected to move west-northwestwards and strengthen into a deep depression on Sunday.

Notably, it could further intensify into a cyclonic storm over the west-central Bay of Bengal by Monday morning, the RMC said. Thereafter, the system is likely to continue moving west-northwestwards and reach the west-central Bay of Bengal off the Andhra Pradesh coast by the morning of 28 October. The forecast does not yet specify a landfall location or time.

What the Forecast Means for Tamil Nadu

With the northeast monsoon active and the Bay of Bengal system gathering strength simultaneously, the combination is likely to sustain and potentially amplify rainfall across multiple parts of Tamil Nadu through the coming days. The convergence of monsoon vigour and a developing cyclonic system is a pattern that has historically led to prolonged heavy spells in the state's southern and delta districts.

Authorities and residents in red- and orange-alert districts are advised to remain prepared for disruption to road, agricultural, and daily activities as the weather system continues to evolve over the next 48 to 72 hours.