Bay of Bengal low brings heavy rain to Tamil Nadu and Kerala, and may become a storm by month end

The first stage is already under way. A cyclonic circulation over the south-west Bay of Bengal and the adjoining Tamil Nadu coast, extending about 5.8 km above sea level, is likely to produce a low-pressure area within 24 hours, with a trough reaching north coastal Andhra Pradesh. A second circulation, over the Gulf of Thailand and parts of Thailand and Myanmar, was expected to move into the northern Andaman Sea as a depression by Wednesday morning.

The second stage is the outlook for 23 October. Conditions favour a low-pressure area over the south-eastern and east-central Bay of Bengal, moving west-north-west. If it intensifies as the department expects, it would become a depression over the central Bay of Bengal by 27 October. Kerala's spell is the longest on the mainland, with very heavy rain forecast there for seven days to 26 October, while Tamil Nadu's is the shortest and sharpest, from 20 to 22 October.

The labels matter because the department uses them for specific wind speeds. A depression has sustained winds of 31 to 49 km an hour, a deep depression 50 to 61 km an hour, and a cyclonic storm 62 to 88 km an hour. A low-pressure area is the stage before all of them. October to December is the main cyclone season for the Bay of Bengal,.

Where the rain is forecast

Data last updated: 21 October 2026, 11:30 AM IST

In the department's scale, heavy rain means 64.5 to 115.5 mm in 24 hours, very heavy rain 115.6 to 204.4 mm, and extremely heavy rain more than 204.4 mm. The Andhra Pradesh outlook is gentler in places: light to moderate rain and thunderstorms over the next three days across coastal Andhra, Yanam and Rayalaseema, with heavy downpours in some areas.

Central and western India, from Madhya Pradesh, Vidarbha and Chhattisgarh to Konkan, Goa and central Maharashtra, can expect rain, thunderstorms and gusty winds from 20 to 23 October. Isolated rain is likely in Nagaland, Manipur, Mizoram and Tripura from 20 to 22 October. In Rajasthan the east sees isolated to scattered rain on 20 and 24 October, and the west on 24 October.

The north turns wet later. Delhi and the NCR stay clear until 23 October, with light rain on 24 and 25 October. Jammu and Kashmir and Ladakh get light to moderate rain at isolated places on 23 to 25 October, Himachal Pradesh on 24 and 25 October, and Uttarakhand from 23 to 26 October. Parts of Punjab, Haryana and Chandigarh may see partly cloudy skies with rain and thunderstorms, though the department has given no dates for those.

Forecasts of this kind shift as a system forms, and the track of a depression a week out can change. Tamil-language news channels are already asking whether it will become a storm. The honest answer on Wednesday morning is that it may, and that the department will say more as the low takes shape.