Heavy rain likely after light showers in Chennai: IMD’s revised forecast explained
After issuing a heavy rainfall alert for Monday, the Regional Meteorological Centre (RMC) in Chennai has now forecast light to moderate rain with light thunderstorms and lightning for several districts this evening. The bulletin, released at 19:00 IST on November 17 (Monday), remains valid until 22:00 IST.
The update comes as families continue tracking Chennai school holiday news for November 18, Tuesday, amid shifting weather conditions.
Rain expected in Chennai and multiple Tamil Nadu districts
According to the RMC, rain and thunderstorm activity is likely at isolated places over:
Ariyalur, Chengalpattu, Chennai, Cuddalore, Kancheepuram, Kanniyakumari, Mayiladuthurai, Nagappattinam, Perambalur, Pudukkottai, Ramanathapuram, Sivaganga, Tenkasi, Thanjavur, Thiruvallur, Thiruvarur, Tirunelveli, Viluppuram, Puducherry and Karaikal.
The bulletin stated that “light to moderate rain with light thunderstorm and lightning is likely.”
Minor disruptions expected
The RMC cautioned that the rain could result in:
- Waterlogging in some areas
- Slippery road surfaces
- Traffic delays in affected districts
What IMD said at 1 pm today
The India Meteorological Department (IMD) issued a detailed weather outlook at 13:00 IST on November 17, 2025, covering Chennai and its neighbouring districts for the next seven days.
Immediate forecast: November 17–19
- Day 1 (Until 08:30 IST on November 18)
Chennai is set to experience a generally cloudy sky with “a few spells of moderate rain with thunderstorm and lightning.”
The 24-hour outlook predicts generally moderate rain with isolated heavy to very heavy rain. A heavy to very heavy rainfall warning remains in effect for Chennai.
Temperatures are expected to reach a maximum of around 27°C, while the minimum may fall to 23–24°C.
- Day 2 (November 18–19)
A generally cloudy sky will persist. One or two spells of light to moderate rain with thunderstorm and lightning are likely.
Overall rainfall is expected to remain light to moderate, with the maximum temperature at around 27°C and the minimum at around 24°C.
The IMD has issued day-wise alerts up to November 23:
- Day 3 (November 19): Light to moderate rain over Tamil Nadu, Puducherry and Karaikal. Heavy rain for Mayiladuthurai and Cuddalore; no Chennai warning.
- Day 4 (November 20): Light to moderate rain at isolated places. Heavy rain again for Mayiladuthurai and Cuddalore.
- Day 5 (November 21): Light to moderate rain at a few places. Heavy rain likely over Chengalpattu, Villuppuram, Mayiladuthurai, Cuddalore, Nagapattinam, and Puducherry & Karaikal.
- Day 6 (November 22): Heavy rain likely at isolated places over Chennai, along with light to moderate rain at a few locations across the region.
- Day 7 (November 23): Heavy rain likely to occur over Chennai at isolated places, with light to moderate rain elsewhere.
- A general thunderstorm and lightning warning is in place from Day 1 to Day 5 across Tamil Nadu, Puducherry and Karaikal.
Why the weather is changing: IMD explains synoptic systems
Two major systems are currently influencing weather over the region:
1. Existing low-pressure area
The low-pressure area that lay over the southwest Bay of Bengal off the Sri Lanka coast has now shifted to the southwest Bay of Bengal and adjoining Sri Lanka as of 08:30 IST on November 17.
It is associated with an upper-air cyclonic circulation and is expected to move slowly west-northwestwards over the next 24 hours.
2. Developing low-pressure system
A fresh low-pressure area is likely to form over the southeast Bay of Bengal around November 22, 2025.
The IMD expects it to move west-northwestwards and intensify further over the following 48 hours.