Chennai, Sep 1 : The Tamil Nadu regional centre of the Indian Meteorological Department (IMD) has predicted heavy to very heavy rains in the districts of Niligiris and Coimbatore on Thursday and Friday. The agency also predicted light to moderate rainfall with lightning and thunderstorms in many parts of Tamil Nadu and Puducherry on Thursday and Friday. Thunderstorm with light rain is likely to occur in some parts of Tamil Nadu during the next 24 hours. The weather department also predicted squally weather with wind speed reaching 40-50 km per hour over Camorin area, Gulf of Mannar, and adjoining Tamil Nadu coast. The weather department has also warned fishermen to not venture into the seas during the period mentioned above. Heavy to very heavy rains are predicted in districts of Nilgiris, Coimbatore, Tiruppur, Theni, Erode, Salem, Karur, Namakkal, and Tiruchi on Thursday and Friday. Chennai district is also expected to receive isolated showers during the day. It may be noted that with the Mettur reservoir being opened, water has gushed into many low-lying areas in Erode district including residences leading to the shifting of the inhabitants of these houses to relief camps opened in the district. More than 500 people are staying in relief camps spread across the district, the administration said. /IANS