Chennai, Jan 31 : The India Meteorological Department (IMD) has predicted heavy to very heavy rains on Wednesday in the Southern and delta districts of Tamil Nadu. A rare winter depression over the south bay of Bengal is likely to bring heavy isolated rains in southern and delta districts, it said. According to the weatherman, the rains could continue up to February 3 with Kanyakumari, Thanjavur, and Nagapattinam districts experiencing heavy rains on February 1, Wednesday. The weather system that causes rains is a rare phenomenon and is a depression over the southeast and adjoining southwest Bay of Bengal. This phenomenon will bring in isolated rains in Southern Tamil Nadu till Thursday and the strength of the rains is likely to dip from Friday. Additional director general of meteorology, S. Balachandran, in a statement said that the weather system in the lower latitude is likely to move east to west direction and another westerly trough in the middle level. The interaction of the easterly and westerly systems will lead to rain. The weather department official said that such weather systems are rare during the second half of January and February. He also cited the example of a severe cyclonic storm at a lower latitude in February 1987. It may be noted that the Bay of Bengal had churned out nine weather systems as depressions or cyclones in the last fifty years in January and February since 1971 but none of them has crossed the Tamil Nadu coast. /IANS