“The depression, which prevailed in the central Bay of Bengal and adjoining northwestern Bay of Bengal yesterday will cross the border between Sagar Island and Sundarbans in a few more hours. A cyclonic circulation lies over south west Bay of Bengal off north Tamil Nadu coast. The sky will be overcast in Chennai and suburbs for the next 48 hours. There may be light rain in a few places in the city,” said RMC Director N Puviarasan.

Heavy rainfall is expected at Villupuram, Kallakurichi and Cuddalore. Also, Chennai, Tiruvallur, Kancheepuram, Chengalpattu, Krishnagiri, Erode, Dharmapuri, Tirupattur, Tiruvannamalai, Salem, Vellore, Ranipet and Villupuram are expected to receive moderate rains. A thunderstorm warning was also issued across areas of Tamil Nadu. Popular weather blogger Pradeep John, who runs the Facebook page Tamil Nadu Weatherman, added that the depression in the Bay would move up north, caught by the westerly trough, and would go West Bengal/Bangladesh coast.

“So the westerly trough dipping from the north dragged the depression away from Andhra Pradesh to West Bengal/Bangladesh. The dry northerlies will meet with the westerlies. This will create very intense thunderstorms, and very good rains,” he said.

In city, the sky conditions are expected to be cloudy. Temperatures are expected to be between 33 degree Celsius and 26 degree Celsius over the next 48 hours.