The low pressure system the weather office had been tracking since midweek finally delivered on Saturday. Kolkata took a proper soaking on 12 September, with the Alipore observatory logging 45.3 mm of rain in the 24 hours to Saturday morning and several sharp spells through the day on top of that. By Saturday evening the familiar pockets of the city were holding water and the India Meteorological Department had extended its rain alert for the state through Sunday, 13 September.
The better news is that the system is on its way out. The IMD expects rainfall over Kolkata and south Bengal to ease from Sunday, with the heaviest activity shifting north to the hills and the Dooars. The city is not out of the wet weather yet, but the worst of this particular spell should be behind us.
What happened on Saturday
The low pressure area formed over the north Bay of Bengal and neighbouring Bangladesh, intensified on Friday, and then drifted towards the northwest Bay, which put Kolkata and the south Bengal coast right in its path of moisture. The result was a day of grey skies, thunderstorms and gusty winds of 30 to 40 kmph in places, with light to moderate rain across the city punctuated by heavier bursts.
Forty-five millimetres in a day is not an extreme figure by Kolkata monsoon standards. The IMD’s own scale only calls rain heavy once it crosses 64.5 mm in 24 hours. What made Saturday awkward was the pattern: rain arriving in intense short spells that outran the drains, on a weekend when shopping crowds were already building ahead of Puja.
The alert for Sunday
The IMD’s warning for Sunday, 13 September, is aimed mainly at north Bengal. Cooch Behar and Alipurduar are flagged for heavy rain, following Kalimpong and Jalpaiguri on Saturday. For Kolkata, the forecast is generally cloudy skies with rain or thundershowers, lightning, and gusty winds reaching 30 to 40 kmph at some places. That is a thunderstorm-day forecast rather than a heavy rain one, and the intensity is expected to drop as the day goes on.
The weather office has also advised fishermen along the West Bengal coast to stay out of the sea while the system passes. If you have a Digha, Mandarmani or Bakkhali trip planned this weekend, expect rough seas and check local advisories before going in the water.
What this means for Kolkata this week
This is the second wet spell in a week. On 8 September the Regional Meteorological Centre at Alipore issued a special bulletin warning of thunderstorms across every south Bengal district and flagged a fresh Bay low pressure area forming around 11 September. That system is the one that arrived on Saturday, so the forecast played out more or less on schedule.
The IMD’s extended outlook for the period to 17 September keeps fairly widespread light to moderate rain and thundershowers in the picture for both north and south Bengal. In plain terms, Kolkata is looking at a typical late monsoon week: not a washout, but afternoons that can turn on you quickly, with the usual waterlogging in low lying stretches after any sharp burst.
Two things are worth keeping an eye on. Pandal construction is well under way across the city, and bamboo frames and stored cloth do not enjoy a week of squalls. And the Blue Line metro is under a maintenance block on Sunday between Mahanayak Uttam Kumar and Shahid Khudiram, so anyone from the southern suburbs switching to autos and buses will be doing it in showery weather. Our monsoon commute survival guide lists the stretches that tend to flood first and how to route around them.
Practical tips
- Plan outdoor errands for the morning. Thunderstorms in this pattern tend to build through the afternoon and evening.
- If lightning starts, get indoors or into a vehicle. Avoid open ground, rooftops, trees and metal hoardings.
- Do not wade through standing water where you cannot see the road. Open manholes and exposed cables are the real risk.
- Two wheeler riders should slow down on stretches with exposed tram tracks and on the flyover approaches, which turn slick within minutes of a shower.
- Puja organisers should tie down loose bamboo and cover stored cloth and lighting before the next burst.
- Check the RMC Kolkata bulletin at mausam.imd.gov.in/kolkata before committing to a long trip. The regional centre updates its warning every day.
Frequently asked questions
How much rain did Kolkata get on Saturday?
The city recorded 45.3 mm in the 24 hours to Saturday morning, 12 September, according to the IMD, with further spells of rain through the day.
Is there a heavy rain warning for Kolkata on Sunday?
No. The heavy rain warning for Sunday covers Cooch Behar and Alipurduar in north Bengal. Kolkata is forecast to have cloudy skies with rain or thundershowers, lightning and gusty winds, with the intensity expected to decrease during the day.
When will the rain stop in Kolkata?
The IMD expects this spell to weaken from Sunday as the low pressure system moves away. Scattered light to moderate rain and thundershowers remain likely across south Bengal through the middle of the coming week, so expect intermittent showers rather than a clean break.
Is it safe to travel to Digha this weekend?
The road trip is fine, but the IMD has asked fishermen to stay out of the sea along the Bengal coast while the system passes, which is a signal that conditions offshore are rough. Stay out of the water and follow instructions from local authorities on the beach.
Will this affect Durga Puja?
Not directly. Durga Puja is in the second half of October, well beyond the range of this forecast. The immediate concern is for half built pandals and stored materials, and for shoppers who are heading out on the weekends leading up to the festival.
The Bottom Line
Saturday was the peak of this spell, and Sunday should be easier, with the heavy rain moving to the hills and Kolkata settling into ordinary thundery monsoon weather. Keep the umbrella in the bag, plan for slow roads if a shower comes through, and give the pandal frames a second look before the next squall. The week ahead is damp rather than dangerous.
Sources: India Meteorological Department forecast and warning for West Bengal issued on 12 September 2026, as reported by PTI and carried by Business Today (12 September 2026), including the Kolkata rainfall figure of 45.3 mm, the district-wise heavy rain warning for north Bengal, the fisherman advisory and the outlook for easing rain from Sunday. IMD Regional Meteorological Centre Kolkata extended range outlook for 11 to 17 September 2026, published at mausam.imd.gov.in/kolkata. Background on the earlier bulletin from Kolkata Dekho’s 9 September weather report.
Featured image: a yellow Kolkata taxi on a rain soaked street, photo by Dibakar Roy on Unsplash.
