IMD forecasts light to moderate rainfall with isolated heavy spells over Tamil Nadu and Puducherry from December 9–11, 2025.
Coastal districts of Tamil Nadu (Chennai, Chengalpattu, Tiruvallur) and Puducherry are likely to experience thunderstorms with lightning and gusty winds of 30–40 kmph.
Day temperatures remain around 27–29°C while nights hover at 23–24°C; humidity levels are at 75–80% during the wet spell.
Weather conditions are expected to improve from December 11 onwards with partly cloudy skies and a gradual return to dry conditions.
The India Meteorological Department has issued a rain forecast for Tamil Nadu and Puducherry, with light to moderate rainfall expected from December 9–11, 2025, following the weakening influence of Cyclone Ditwah and a lingering monsoon trough over the Bay of Bengal. Coastal districts, including Chennai, Chengalpattu, Tiruvallur, Villupuram, and Cuddalore in Tamil Nadu, along with Puducherry and Karaikal, are likely to experience isolated heavy rainfall spells accompanied by thunderstorms and lightning. Day temperatures are settling around 27–29°C, while nights remain cool at 23–24°C, with humidity levels elevated at 75–80%, providing muggy conditions.
IMD Alerts and Rainfall Forecast
The IMD has warned of light to moderate rainfall with isolated heavy showers at a few places over coastal Tamil Nadu and Puducherry over the next 48–72 hours, continuing from the recent Cyclone Ditwah episode. Thunderstorms accompanied by lightning and gusty winds reaching 30–40 kmph are likely in isolated places, particularly during the afternoon and evening hours. The weather system is expected to gradually weaken after December 10, with conditions improving significantly from December 11 onwards as the monsoon trough shifts eastwards and weakens.
Regional Impact and Waterlogging
North Chennai and low-lying coastal areas remain vulnerable to waterlogging if heavy rainfall occurs, though the expected rainfall is lighter than the recent Cyclone Ditwah episode. Civic authorities have advised residents to remain cautious and continue monitoring drainage systems, particularly in areas that experienced severe flooding just days earlier. Agricultural areas in southern districts may benefit from the additional rainfall for standing rabi crops, though excessive waterlogging could damage germinated seeds.
Temperature and Weather Dynamics
Minimum temperatures in coastal Tamil Nadu are expected to remain around 23–24°C, while interior districts may see slightly cooler readings of 22–23°C. Humidity levels remain high at 75–80% throughout the wet spell, creating a damp atmosphere particularly in coastal zones. Wind speeds of 20–30 kmph from the northeast are maintaining moisture influx, sustaining the potential for scattered rain and thunderstorm development, especially over coastal and deltaic regions.
Weekly Forecast and Return to Normalcy
The rain is expected to taper off significantly from December 11, with partly cloudy skies becoming increasingly prevalent, and dry weather expected to prevail over most parts of Tamil Nadu and Puducherry by December 12–13. Temperatures are forecast to rise slightly with maximums touching 28–30°C in coastal areas and 26–28°C in interior regions by mid-next week. The overall pattern suggests a gradual transition from the recent wet spell to more typical December conditions with clearer skies, lower humidity, and more comfortable daytime temperatures.
