Northeast monsoon, which accounts for a major share of Tamil Nadu’s annual rainfall, is likely to set in over the south peninsula in the next two to three days. It will coincide with the withdrawal of Southwest monsoon from the remaining parts of the country, the Regional Meteorological Centre (RMC) has said.

Rainfall in Tamil Nadu is expected to gradually increase from Wednesday and cover many weather stations, with fairly widespread rain from Thursday. As in the past, this year too is headed for simultaneous withdrawal of Southwest monsoon and start of Northeast monsoon.

Meanwhile, traders at the Koyambedu wholesale market hope the rainfall increase would improve vegetable supplies and help to stabilise prices in two weeks.

The RMC is closely monitoring the weather system that is likely to influence the formation of a low pressure area over the Southeast Bay of Bengal on Tuesday. Officials said favourable conditions for the monsoon to set in would depend on the system’s development and path.

The prevailing upper air cyclonic circulation over the Gulf of Mannar and the adjoining south Tamil Nadu coast will sustain the current wet spell in the State. On Tuesday, Cauvery delta and southern districts, including Thanjavur and Kanniyakumari, would receive light to moderate rainfall, with winds gusting up to 40-50 kmph.

The rainfall is expected to extend to north coastal and interior districts, including Chennai and Dindigul, on Wednesday and turn heavy in some districts from October 15. Heavy rain in various parts of the State may last until October 18.

The State may get relief from the above-average temperatures after October 15. On Monday, Vellore recorded the highest maximum temperature in the State at 36.7 degrees Celsius. Chennai has chances of light to moderate rain in some areas on Tuesday.

The increase in rainfall has sparked hopes of a drop in vegetable prices, which recorded a sharp rise in recent weeks. Traders at the Koyambedu wholesale market said the cost of onions had stayed stable, at ₹60 a kg, for the past few days. Tomatoes were selling at ₹30-₹40 a kg. Some more vegetables, like bitter gourd and beans, were sold for around ₹60 a kg.

P. Sukumaran, treasurer, Koyambedu Vegetables, Fruits and Flowers Merchants’ Association, said low yields in Andhra Pradesh and Karnataka also affected supplies and pushed up the prices. A bunch of coriander leaves was sold for ₹50. “Deficit rainfall in neighbouring States has led to shortage of supplies. We expect improved rainfall to help the prices ease in the next two weeks,” he said.