Tamil Nadu rain alert: 16 districts on watch, heavy showers in Nilgiris and Coimbatore
Synopsis
A trough stretching from Karnataka to the Gulf of Mannar and an upper-air circulation over coastal Andhra Pradesh are combining to drench Tamil Nadu through the weekend. Sixteen districts are on alert Thursday, activity peaks across the north on Saturday, and fishermen face a no-sail advisory until Sunday — a week-long weather event that will affect millions across the state.
Key Takeaways
The RMC has placed 16 Tamil Nadu districts , including Chennai , on alert for moderate rain and thunderstorms on Thursday, 18 September .
Heavy rain is forecast in isolated locations across the Nilgiris , Coimbatore , Karur , Tiruchirappalli , Perambalur , Ariyalur , and Thanjavur on Thursday.
Gusty winds of 40–50 kmph are expected to accompany thunderstorms across affected districts.
Rainfall is set to intensify across 11 northern districts on Saturday , then shift south on Sunday .
Fishermen advised against entering the Bay of Bengal and Andaman Sea until Sunday ; winds may reach 65 kmph .
Light to moderate rain likely across Tamil Nadu through Tuesday ; no warning issued for the Tamil Nadu coast or Arabian Sea.
The Regional Meteorological Centre (RMC) has forecast widespread rain across Tamil Nadu on Thursday, 18 September 2026, placing 16 districts — including Chennai, Tiruvallur, Chengalpattu, and Kancheepuram — on alert for moderate showers accompanied by thunderstorms and gusty winds. Fishermen have been advised to stay off parts of the Bay of Bengal and the Andaman Sea until Sunday.
Weather Systems Driving the Rain
According to the RMC, a trough extends at approximately 0.9 km above mean sea level, running from north interior Karnataka through south interior Karnataka and Tamil Nadu down to the Gulf of Mannar. An additional upper-air circulation persists over coastal Andhra Pradesh and adjoining Rayalaseema at around 1.5 km above sea level. These two converging systems are together responsible for the heightened rainfall activity across the region.
Districts on Heavy Rain Alert Thursday
Heavy rain is forecast at isolated places in the Nilgiris, Coimbatore, Karur, Tiruchirappalli, Perambalur, Ariyalur, and Thanjavur districts on Thursday. Thunderstorms, lightning, and gusty winds reaching speeds of 40 to 50 kmph may accompany the rainfall across these areas.
Moderate rain is expected at several places in Chennai, Tiruvallur, Chengalpattu, Kancheepuram, Ranipet, Vellore, Tirupattur, Salem, Tiruppur, Erode, Krishnagiri, Dharmapuri, Namakkal, Kallakurichi, Madurai, and Sivaganga. Light rain is likely elsewhere in Tamil Nadu and in Puducherry.
Chennai Outlook and Temperatures
The city of Chennai and its suburbs will see partly cloudy skies on Thursday, with light to moderate rain and thunderstorms likely during the evening or night hours. The maximum temperature is expected to hover between 35°C and 36°C, while the minimum may range from 27°C to 28°C. Residents have been advised to remain cautious during evening commutes due to the probability of sudden squalls.
Extended Forecast Through Next Week
Rainfall activity is expected to intensify across northern Tamil Nadu on Saturday, with heavy showers forecast in 11 districts including Tiruvallur, Vellore, Ranipet, Tirupattur, Tiruvannamalai, Salem, Dharmapuri, and Krishnagiri. By Sunday, heavy rain is likely to shift toward western, central, and southern Tamil Nadu, with the Nilgiris, Coimbatore, Dindigul, Theni, Madurai, Sivaganga, Pudukkottai, and Tiruchirappalli among the affected districts. Light to moderate rain is likely to persist across the state through Tuesday. On Friday, isolated heavy rain has been forecast for the Nilgiris and Coimbatore districts alone.
Sea Conditions and Fishermen Advisory
The RMC has advised fishermen not to venture into parts of the Bay of Bengal and the Andaman Sea until Sunday, as winds in those areas could reach 65 kmph. No coastal warning has been issued for the Tamil Nadu coast or the Arabian Sea at this time, indicating conditions closer to shore remain manageable.
Authorities and residents in rain-hit districts are advised to stay updated with RMC bulletins as the weather system evolves through the weekend.
Point of View
Not just a Thursday advisory.
NationPress
17 Sept 2026
Frequently Asked Questions
Which Tamil Nadu districts are on rain alert on 18 September 2026?
Sixteen districts are on alert for moderate rain and thunderstorms on 18 September, including Chennai, Tiruvallur, Chengalpattu, Kancheepuram, Ranipet, Vellore, Tirupattur, Salem, Tiruppur, Erode, Krishnagiri, Dharmapuri, Namakkal, Kallakurichi, Madurai, and Sivaganga. Heavy rain has additionally been forecast at isolated places in the Nilgiris, Coimbatore, Karur, Tiruchirappalli, Perambalur, Ariyalur, and Thanjavur.
What is causing the heavy rain in Tamil Nadu this week?
The rain is driven by two weather systems: a trough extending from north interior Karnataka to the Gulf of Mannar at about 0.9 km above mean sea level, and an upper-air circulation over coastal Andhra Pradesh and Rayalaseema at about 1.5 km above sea level. Together, these systems are generating widespread rainfall and thunderstorm activity across the state.
What is the Chennai weather forecast for Thursday?
Chennai will see partly cloudy conditions on Thursday with light to moderate rain and thunderstorms likely in the evening or at night. The maximum temperature is expected between 35°C and 36°C, and the minimum between 27°C and 28°C.
Is there a warning for fishermen in Tamil Nadu?
Yes, the RMC has advised fishermen not to venture into parts of the Bay of Bengal and the Andaman Sea until Sunday, 21 September, as winds could reach 65 kmph in those areas. No separate warning has been issued for the Tamil Nadu coast or the Arabian Sea.
How long will the rain last in Tamil Nadu?
Light to moderate rain is expected across Tamil Nadu through Tuesday. Rainfall is forecast to peak across northern districts on Saturday, shift to western, central, and southern districts on Sunday, and then gradually ease into the following week.
