Rains will continue to batter Tamil Nadu for the next seven days and the next 48 hours are “very crucial”, the India Meteorological Department (IMD) today said.

IMD Director General Laxman Singh Rathore attributed the heavy rains to a “trough of low” over Southwest Bay of Bengal off Tamil Nadu and Sri Lanka coast which will continue to bring rains over the next three days. Thereafter, the state will see an anti-cyclone activity which will be associated with “heavy rains” at some places.

“The phenomenon will continue for the next seven days, but the next 48 hours are very crucial. Neighbouring states will also see rainfall activity,” Rathore said.

He said the Union Home Secretary Rajiv Mehrishi chaired a high-level meeting with the “stake holders”, including officials of National Disaster Management Authority, which was attended by Tamil Nadu Chief Secretary through a video conference. The IMD also briefed about the weather forecast.

A warning has also been issued for coastal districts of Tamil Nadu, Puducherry, Andhra Pradesh (especially Nellore and Chittoor), interior Tamil Nadu and Rayalseema region of Andhra Pradesh.

Northeast monsoon

The period October to December is referred to as Northeast Monsoon season over peninsular India. It is a major period of rainfall activity over the southern peninsula, particularly Coastal Andhra Pradesh, Rayalaseema, Tamil Nadu and Puducherry.

For Tamil Nadu this is the main rainy season accounting for about 48 per cent of the annual rainfall. Coastal districts of the state get nearly 60 per cent of the annual rainfall and the interior districts about 40-50 per cent of the precipitation.

However, this season Tamil Nadu alone has witnessed 50 per cent excess rainfall by December 1 itself. “Almost all districts of Tamil Nadu have received excess rainfall ranging from 10 to 150 per cent,” Rathore said.

According to the IMD data, Chennai has seen 89 per cent more than normal rainfall this season, while the districts of Kancheepuram, Tiruvallur, Vellore and Tirunveliveli received 154 per cent, 139 per cent, 136 per cent and 110 per cent excess precipitation respectively so far.