CHENNAI: A day before the onset of the Northeast Monsoon over the southern peninsula on Thursday, widespread light rain was recorded across Chennai and its surrounding suburbs. According to the Regional Meteorological Centre (RMC), isolated places in Nilgiris, Coimbatore, Theni, and Virudhunagar districts are expected to receive heavy to very heavy rainfall on Thursday.

The weather department stated that an upper-air cyclonic circulation over the Southwest Bay of Bengal, off the South Sri Lanka coast, now lies over the Comorin area coast and extends up to 1.5 km above mean sea level. Additionally, an easterly trough runs from this cyclonic circulation over the Comorin area to the Northwest Bay of Bengal off the Odisha coast, across the Gulf of Mannar, extending up to 1.5 km.

The RMC noted that heavy rain is likely at isolated places over Mayiladuthurai, Nagapattinam, Tiruvarur, Thanjavur, Cuddalore, Tenkasi, Kanniyakumari, Kallakurichi, Salem, Tiruchy, Kancheepuram, Chengalpattu, Ranipet, Tiruppur, and Dindigul, along with Puducherry and Karaikal. Chennai is set to experience moderate rainfall accompanied by thunderstorms and lightning in some areas on Thursday.

Widespread heavy rainfall at isolated places, along with thunderstorms, lightning, and gusty winds reaching speeds of 40–50 km/h, is expected across the state until October 20.

On Friday, heavy rain at isolated places with thunderstorms, lightning, and gusty winds 40–50 kmph is likely over Nilgiris, Coimbatore, Erode, Tiruppur, Dindigul, Theni, Virudhunagar, Tenkasi, Kanniyakumari, Ramanathapuram, Sivaganga, Tiruchy, Namakkal, Dharmapuri, Krishnagiri, Salem, Tiruvannamalai, Kallakurichi, Villuppuram, Chengalpattu, Kancheepuram, Ranipet, Tiruvallur, Chennai, Cuddalore, Mayiladuthurai, Nagapattinam, Tiruvarur, and Thanjavur districts, as well as Puducherry and Karaikal.

On October 17, isolated heavy rainfall accompanied by thunderstorms, lightning, and gusty winds of 40–50 kmph is expected in Nilgiris, Coimbatore, Theni, Dindigul, Madurai, Tiruppur, Kancheepuram, Ranipet, Kallakurichi, Mayiladuthurai, Nagapattinam, Tiruvarur, Thanjavur, Cuddalore, Erode, Dharmapuri, and Krishnagiri districts, as well as Puducherry and Karaikal. On October 18, heavy rain will continue over Nilgiris, Coimbatore, Mayiladuthurai, Thanjavur, Tiruvarur, and Nagapattinam.