The 2026 north-east monsoon swept into the South Peninsula on Thursday, with India Meteorological Department (IMD) warning of isolated very heavy rainfall over Tamil Nadu, Puducherry and Karaikal on Thursday and Friday, Kerala and Mahe on Thursday, and South Interior Karnataka on Friday.

The seasonal rains arrived just as the IMD declared the south-west monsoon’s withdrawal from entire country, leaving behind a rainfall deficit. But network of intersecting troughs and cyclonic circulations had already fallen into place over adjoining seas and land, priming the region for a wet opening spell of north-east monsoon.

Video Credit: Businessline

A cyclonic circulation lingering over the Gulf of Mannar shifted towards south coastal Tamil Nadu. From there, a trough extended across southwest and west-central Bay of Bengal to north-west Bay off the Odisha coast. This broad zone of lower pressure offered moisture-laden easterlies and northeasterlies a pathway to converge and feed rain along the eastern seaboard, from Tamil Nadu and Puducherry to Andhra Pradesh and Odisha.

The configuration could prove more useful to agriculture than a burst of concentrated rain. A persistent trough in the easterlies can sustain rising air and repeated showers across a broad corridor, allowing soil moisture to recover over several days. A compact low-pressure system or depression, by contrast, can unleash intense rain over a shorter spell, overwhelming drainage, inundating fields and damaging crops nearing harvest. The distinction may not be not absolute here: a slow-moving depression can also deliver widespread rain.

A second trough stretched from north-east Uttar Pradesh to the east-central Arabian Sea across eastern Madhya Pradesh and Maharashtra. A third extended from a cyclonic circulation over the south-east Arabian Sea and adjoining Lakshadweep towards north-west Arabian Sea, adding another zone of convergence. 

Isolated heavy rain is likely over Kerala and Mahe for six days, and over Tamil Nadu, Puducherry and Karaikal for five days from Saturday. Coastal Karnataka is in line for heavy rain on Friday and Saturday, while South Interior Karnataka faces a prolonged spell from Saturday after Thursday’s forecast rain. Coastal Andhra Pradesh, Yanam and Rayalaseema are on alert for Thursday and Friday, with Telangana entering the picture on Sunday.

Western Ghats could bear the brunt of the opening spell. European Centre for Medium-Range Weather Forecasts has flagged the Ghats straddling Tamil Nadu and Kerala for some of the heaviest rain through Friday. Udhagamandalam, Coimbatore, Valparai, Dindigul, Madurai and Sivakasi are among the areas to watch in western and southern Tamil Nadu. Tirunelveli, Panangudi and Nagercoil in the south are also in firing line.

Rain threats extend eastward to Salem, Namakkal, Chennai, Tambaram, Thiruporur, Kanchipuram and Kalpakkam, along with the Cauvery delta districts. Tirupati, Visakhapatnam, Chirala and Machilipatnam in Andhra Pradesh, and Brahmapur and Bhubaneswar in Odisha, are also in line for heavy rain during the onset phase. Karnataka’s Western Ghats districts, including Chikkamagaluru, Shivamogga and Hassan, could also share the wet spell.

Published on October 15, 2026