North-East Monsoon Brings Heavy Rain to South Peninsula Starting October 15

The north-east monsoon for 2026 has officially begun to affect the South Peninsula of India as of Thursday, October 15, according to the India Meteorological Department (IMD). The weather office has issued warnings about isolated very heavy rainfall over Tamil Nadu, Puducherry, and Karaikal on Thursday and Friday, as well as over Kerala and Mahe on Thursday. South Interior Karnataka is also expected to see significant rain on Friday.

This development coincides with the IMD's declaration that the south-west monsoon has withdrawn from the entire country, leaving behind a rainfall shortfall in some regions. However, a network of intersecting troughs and cyclonic circulations has already formed over the adjacent seas and land areas, setting the stage for a wet start to the north-east monsoon season.

Weather Systems Driving the Rainfall

A cyclonic circulation that had been stationary over the Gulf of Mannar has now shifted toward south coastal Tamil Nadu. From this circulation, a trough extends across the southwest and west-central Bay of Bengal to the northwest Bay near Odisha's coast. This broad low-pressure area facilitates the flow of moisture-laden easterly and northeasterly winds, promoting rainfall along the eastern coastline stretching from Tamil Nadu and Puducherry to Andhra Pradesh and Odisha.

Such a configuration tends to favor steady and widespread showers rather than isolated intense downpours. A persistent trough in the easterly winds supports continuous rising air and repeated rainfall over a large area, which helps replenish soil moisture gradually—beneficial for agriculture. In contrast, a compact low-pressure system or depression can cause short bursts of heavy rain that may overwhelm drainage systems and damage crops close to harvest. Still, a slow-moving depression can also produce widespread rains over a longer period.

Additional Rainfall Zones and Duration

Besides the trough over the Bay of Bengal, another trough stretches from northeast Uttar Pradesh to the east-central Arabian Sea, passing through eastern Madhya Pradesh and Maharashtra. A third trough extends from a cyclonic circulation over the southeast Arabian Sea and nearby Lakshadweep toward the northwest Arabian Sea, creating multiple convergence zones that enhance rainfall potential.

Kerala and Mahe are forecast to experience isolated heavy rains for six days starting Thursday. Tamil Nadu, Puducherry, and Karaikal face a similar outlook for five days beginning Saturday. Coastal Karnataka is likely to receive heavy rainfall on Friday and Saturday, while South Interior Karnataka is expected to undergo a prolonged wet spell starting Saturday following some rain on Thursday. Coastal Andhra Pradesh, Yanam, and Rayalaseema are on alert for rain on Thursday and Friday, with Telangana expected to see rain from Sunday onwards.

Impact on the Western Ghats and Key Districts

The Western Ghats mountain range, known for its ecological significance and influence on regional weather, is anticipated to bear the brunt of the initial monsoon rains. The European Centre for Medium-Range Weather Forecasts (ECMWF) highlights the Ghats spanning Tamil Nadu and Kerala as areas likely to receive significant rainfall through Friday. Towns such as Udhagamandalam, Coimbatore, Valparai, Dindigul, Madurai, and Sivakasi in western and southern Tamil Nadu are among those to watch. Further south, Tirunelveli, Panangudi, and Nagercoil are also forecast to experience heavy showers.

East of the Ghats, rainfall threats extend to regions including Salem, Namakkal, Chennai, Tambaram, Thiruporur, Kanchipuram, and Kalpakkam, along with the Cauvery delta districts, which are vital agricultural zones. In Andhra Pradesh, Tirupati, Visakhapatnam, Chirala, and Machilipatnam are expected to receive heavy rains, while Brahmapur and Bhubaneswar in Odisha are also on the forecast radar. Karnataka’s Western Ghats districts such as Chikkamagaluru, Shivamogga, and Hassan are poised to share in the wet conditions during this onset phase.

Context and Importance

The north-east monsoon plays a crucial role in replenishing water resources and supporting agriculture in southern and eastern parts of India. This monsoon typically begins in October and lasts through December, bringing much-needed relief after the withdrawal of the south-west monsoon. The timely arrival and distribution of rain during this season can significantly influence crop yields, water reservoir levels, and overall regional climate conditions. Monitoring these weather patterns helps farmers, policymakers, and residents prepare for the impacts and benefits of the monsoon season.

As the 2026 north-east monsoon progresses, meteorologists will continue to track the intensity and spread of rainfall to provide updates and warnings. Staying informed will be crucial for managing agricultural activities, water resources, and local infrastructure in the affected states.