The India Meteorological Department has issued an orange alert for six districts in Tamil Nadu on Saturday, 18 October 2025, forecasting heavy to very heavy rainfall as the Northeast Monsoon brings widespread showers across the state. An atmospheric disturbance over the Tamil Nadu region following the monsoon's onset is driving the prevailing wet conditions.

Districts Under Orange Alert

The six districts facing the highest rainfall intensity on Saturday are Tiruvallur, Kancheepuram, Ranipet, Villupuram, the Nilgiris, and Coimbatore. Heavy rain has also been forecast for Chennai and neighbouring Chengalpattu, though the orange alert — indicating the possibility of very heavy showers — applies specifically to the six districts listed above.

Broader Rainfall Pattern Across the State

A wide belt of Tamil Nadu is expected to receive heavy showers during the day. Districts including Tirunelveli, Kanyakumari, Theni, Dindigul, Madurai, Tiruppur, Vellore, and Kallakurichi are among those forecast to receive heavy rain. The delta region — comprising Mayiladuthurai, Nagapattinam, Tiruvarur, and Thanjavur — has also been flagged for heavy rainfall, alongside Erode, Dharmapuri, Krishnagiri, and Salem in the western and northwestern parts of the state.

Spells of strong rain accompanied by gusty winds have been forecast for Ramanathapuram, Tiruchirappalli, Namakkal, Cuddalore, Karur, Perambalur, and Ariyalur. Moderate rainfall with strong winds is likely in the remaining parts of the state, indicating that wet and windy conditions will be widespread through Saturday.

Two-Day Outlook: Rain to Continue on Sunday

The weather department expects rainfall to persist in several districts on Sunday, 19 October 2025. The Nilgiris faces heavy to very heavy rain on Sunday as well, making it one of the districts at risk on consecutive days. Heavy rain has also been forecast for Coimbatore, Erode, Namakkal, Ranipet, Tiruvallur, and Tirupattur on Sunday. Notably, Coimbatore, Ranipet, and Tiruvallur feature in the warnings for both days, though Saturday's forecast indicates the possibility of greater intensity in those districts.

Northeast Monsoon Onset and Context

The Northeast Monsoon, which typically sets in over Tamil Nadu in early October, is the primary source of rainfall for the state and parts of coastal Andhra Pradesh and Puducherry. This season's onset has already brought widespread rain across northern, western, and southern Tamil Nadu. The current two-day warning reflects the uneven spatial distribution characteristic of Northeast Monsoon spells, with the strongest showers concentrated in select districts while moderate rain covers much of the state. Authorities in the affected districts are expected to remain on standby for flood-related response, particularly in low-lying coastal areas and the Nilgiris hill district, which is historically vulnerable to landslides during intense rainfall events.