2 min readBengaluruUpdated: Oct 15, 2026 04:51 PM ISTThe northeast monsoon affects Tamil Nadu, Puducherry, Karaikal, Yanam, Rayalaseema, coastal Andhra Pradesh, Kerala, Mahe and south interior Karnataka. (Representational image)The India Meteorological Department (IMD) on Thursday declared the onset of the northeast monsoon over southern peninsular India, marking an early arrival ahead of its normal onset date of around October 20.There will be heightened rainfall activity along with gusty winds, thunder and lightning over Kerala, coastal and southern Karnataka, Tamil Nadu, Puducherry, Mahe, Karaikal and along the coastal belt of Andhra Pradesh through October 18, the IMD said.Also known as the winter monsoon, the northeast monsoon lasts from October to December and affects Tamil Nadu, Puducherry, Karaikal, Yanam, Rayalaseema, coastal Andhra Pradesh, Kerala, Mahe and south interior Karnataka. Tamil Nadu receives nearly half of its annual rainfall during the season.Earlier this month, the Met department released the northeast monsoon forecast which mentioned normal rainfall, which is expected to be 88 per cent of the long period average of 334.1mm (1971-2020).Also Read | Monsoon ends with 13% rain deficit, driest year in a decadeAccording to the IMD, a cyclonic circulation prevails over southern Tamil Nadu, which will further contribute to the increase in intense rainfall.Thursday also marked the complete withdrawal of the southwest monsoon on Thursday. This year, the seasonal rainfall ended 13 per cent below normal primarily under the influence of the intensifying El Niño conditions in the Pacific Ocean making 2026 the fourth driest monsoon since 2001.