The India Meteorological Department (IMD) has forecast heavy rain accompanied by strong winds in Nilgiris, Coimbatore, and Erode districts of Tamil Nadu on Thursday, 1 October, as an active weather trough stretching from the south interior of Karnataka to the Gulf of Mannar through the state is expected to intensify rainfall across multiple districts.

Key Weather Feature Driving the Rain

The primary trigger for Thursday's widespread rainfall is a persistent trough running from south interior Karnataka through Tamil Nadu to the Gulf of Mannar. Under its influence, the three western districts — Nilgiris, Coimbatore, and Erode — are expected to bear the brunt of the heaviest showers, the department said. Strong winds are also likely to accompany the rain in these areas.

This weather pattern is consistent with the transition into the northeast monsoon season, which typically begins influencing Tamil Nadu in early October, bringing a shift in rainfall distribution from the western to the eastern and coastal belts of the state.

Districts on Moderate Rain and Thunderstorm Watch

Beyond the three high-alert western districts, several inland and southern districts have been placed under a moderate rain and thunderstorm forecast. Tiruchirappalli, Namakkal, Theni, Tenkasi, Tirupattur, Dindigul, Madurai, and Virudhunagar are all expected to receive moderate showers with thunder and lightning. Tirunelveli and Kanyakumari districts are also likely to see moderate rainfall accompanied by lightning.

The department has forecast light to moderate showers at scattered locations across the remaining parts of Tamil Nadu, indicating that rainfall will not be uniform across the state.

Puducherry, Karaikal and Chennai Outlook

In the union territories, Puducherry and Karaikal are expected to receive light to moderate showers similar to conditions forecast for much of Tamil Nadu's coastal belt. For Chennai, the department has projected only a chance of light rain during the evening or night hours — significantly milder than the heavy rainfall warned for western districts. No heavy rain advisory has been issued for the state capital.

Varying Intensity Across the State

Thursday's forecast underscores sharply differing conditions across Tamil Nadu's geography. Western and hill districts face the highest risk from heavy rain and gusty winds, while central, inland, and southern districts can expect thunderstorm activity. Coastal and northern plains, including Chennai, are likely to see only scattered light showers. Residents and commuters in Nilgiris, Coimbatore, and Erode have been implicitly urged to remain cautious given the combination of heavy rain and strong winds forecast for the day.

With the trough forecast to persist through Thursday, conditions could evolve, and the department's updates through the day will be critical for affected districts.