Chennai, Nov 21 : The Indian Meteorological Department (IMD) has said that low pressure over the central parts of the South Bay of Bengal has turned into a depression and would lead to heavy rains in isolated areas of Chennai and North Tamil Nadu, Karaikal, and Puducherry. Certain areas of South Tamil Nadu is also expected to receive light to moderate rains with thunderstorms and lightning. The IMD said that on November 21, Villupuram, Chengalpattu, Kancheepuram, Chennai, Ranipet, and Tiruvallur districts of Tamil Nadu will receive heavy rains while on November 22 Tiruvallur, Kancheepuram, Ranipet, and Vellore districts may receive heavy rains. A senior official with the IMD told IANS that rains will occur in Chennai and adjoining districts with thunder and lightning. The maximum and minimum temperatures are likely to be around 28 degree Celsius and 22-23 degrees Celsius respectively. Fishermen are advised not to venture out into the sea on November 21 and November 22. It may be noted that since the arrival of the northeast monsoon, Tamil Nadu has received copious rains and most of the water tanks in the state are full. Some lakes have discharged water as the rains in the catchment areas were bringing in more water to the tanks. /IANS