Seven districts in Tamil Nadu are on alert for very heavy rainfall on Tuesday, 20 October, while Chennai and a broad swathe of the state face heavy showers, according to the Regional Meteorological Centre (RMC), Chennai. Gusty winds of up to 50 km/h are expected to accompany the intense spells in the worst-hit areas.

Districts Under Very Heavy Rainfall Warning

The RMC has placed Pudukkottai, Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai, Cuddalore and Villupuram under a very heavy rainfall alert for Tuesday. These districts sit within the Cauvery delta belt and along the coastline — zones historically vulnerable to intense precipitation during the northeast monsoon season.

The weather department attributed the conditions to an upper-air cyclonic circulation over the southwest Bay of Bengal, positioned off the north Tamil Nadu coast. A trough extending from this circulation towards the northwest Bay of Bengal is further amplifying rainfall across the region.

Heavy Rain Likely Across Chennai and Multiple Other Districts

Beyond the seven districts on high alert, heavy showers are forecast across a significantly wider stretch of the state. Districts expected to receive heavy rain on Tuesday include Tiruvallur, Kancheepuram, Chengalpattu, Tiruchirappalli, Ariyalur, Perambalur, Ranipet, Vellore and Tirupattur in the north and centre.

In the south, Theni, Dindigul, Madurai, Virudhunagar and Ramanathapuram are also covered under the heavy rainfall forecast. For Chennai specifically, the RMC has predicted heavy rain with thunderstorms and lightning at one or two isolated locations during Tuesday evening — indicating that intense spells within the city are likely to be localised rather than uniformly widespread.

Wednesday Outlook: Focus Shifts to Southern Tamil Nadu

The two-day forecast indicates a geographical shift in the zone of most intense rainfall by Wednesday, 21 October. Theni, Tenkasi, Virudhunagar, Tirunelveli and Kanyakumari are likely to experience very heavy showers on that day, according to the department's extended outlook.

Heavy rainfall is additionally forecast on Wednesday for Pudukkottai, Thanjavur, Tiruvarur, Nagapattinam and Mayiladuthurai, alongside Madurai, Dindigul, Thoothukudi and Ramanathapuram. The delta districts that dominate Tuesday's very heavy rainfall warning give way to southern coastal and inland districts as the primary concern for Wednesday.

What Residents and Authorities Should Note

The RMC's distinction between 'very heavy' and 'heavy' rainfall categories carries administrative significance — the former typically triggers district-level precautionary measures including school closures, fishermen advisories and flood-control alerts in low-lying areas. This comes amid the peak of Tamil Nadu's northeast monsoon season, when the state draws the bulk of its annual rainfall and delta districts face the highest flood risk. Residents in alert zones are advised to stay updated with official bulletins as the system evolves over the next 48 hours.