The low pressure area over equatorial Indian Ocean and adjoining southwest Bay of Bengal had become 'well-marked' and lay over the southwest Bay of Bengal and adjoining Sri Lanka, an IMD bulletin said.
"The system is likely to move northwestwards and concentrate into a depression during next 24 hours. It is likely to continue northwestwards and further concentrate into a deep depression and cross Tamil Nadu coast between Pamban and Nagapattinam around May 17 morning," it said.
Already several interior parts in the state have started receiving summer rains.
In the last 24 hours ended 8.30 AM today, Avinasi (Tirupur dt) and Eraniel (Kanyakumari dt) received 5 cm each while Periyanaickenpalayam (Coimbatore) and Vedaranyam (Nagapattinam) recorded 4 cm each rainfall.
Good rainfall was also recorded at several places in Coimbatore, Nilgiris, Tirunelveli, Erode, Thoothukudi and Madurai districts, the weather office said.