The transition time between Southwest Monsoon and Northeast Monsoon always throws up some of the most intense thunderstorms of the season in the interior places of Peninsular India. Yesterday was no surprise with many places in South Tamil Nadu recording very heavy rains particularly around Madurai, Theni & Virudhunagar districts. It was a welcome relief for the people out there who were enduring one of the hottest second summers in recent times as many places touched record max temperatures. 
Not often one gets to see almost 15 districts recording at least 20 mm during off season. In a list that could possibly put a Northeast Monsoon daily rainfall report to shade yesterday has seen widespread rains in South Tamil Nadu. Along with South TN parts of Western Tamil Nadu also got benefited from the thunderstorms yesterday with placs in Tiruppur & Coimbatore district recording rains that cooled down the region
After 3 days of heavy rains things could ease down today with the rain bands narrowing to a small patch over extreme southern Peninsular India. While parts of North Kerala around the Wayanad region, South Interior Karnataka around the Cauvery Catchment region and Nilgiris district of Tamil Nadu could get moderate to heavy rains in isolated places overall heavy rains are less likely over vast parts of the region.
In the meanwhile Western Pacific holds the key for the Northeast Monsoon prospects as numerical models expect a pair of strong typhoons holding the control over evolving wind pattern in the Indo China & Bay of Bengal region. While the Anti Cyclonic Circulation over Northwest India that heralded the withdrawal of Southwest Monsoon from the Indian Subcontinent will bring the winds to North Northeasterly the strong typhoons are likely to retain the winds over Bay as westerlies making it difficult for the onset of Northeast Monsoon over the next week to ten days.
While the NNE winds will ensure the hot conditions that was prevailing over most part of the state will ease over the next day or two the presence of the dry continental air from the ACC over Northwest India will also minimize the rainfall prospects during this period.
While there is nothing to panic yet but as things are evolving now we could possibly see a slight delay in the onset of Northeast Monsoon over Tamil Nadu.