Kolkata has recorded 1,718.9mm of rain between June and September during the 2026 monsoon, registering a 28% surplus despite an El Nino-linked rainfall deficit across India. The total makes this the city’s second-highest monsoon rainfall in the past decade, according to the Regional Meteorological Centre in Kolkata.
The seasonal benchmark for Kolkata by the end of September is 1,345.5mm. This year’s total is also higher than the 1,659.2mm recorded during the 2025 monsoon, but remains below the 1,769.8mm recorded in 2021, the wettest monsoon in the city during the past decade.
The rainfall pattern was driven by repeated weather systems forming over the Bay of Bengal, which kept monsoon activity over Kolkata and much of south Bengal active through most of the season. HR Biswas, head of the Regional Meteorological Centre Kolkata, said these systems influenced both the volume and distribution of rainfall across the region.
Southwest monsoon reached Kolkata on June 12, within its normal onset period. June recorded 364.6mm against a monthly average of 282.9mm. July, normally the city’s wettest month, was the only month to post a deficit, with 340.8mm compared with an average of 387.4mm.
Rainfall increased again in August, which recorded 424.4mm against an average of 364mm. September was the wettest of the four months, with 589.2mm compared with a monthly average of 311mm. The city received rain on 20 days during the month, including 123mm recorded at the Alipore Met office on September 2.
The surplus has come despite El Nino conditions, which are associated with unusually warm Pacific Ocean waters and weaker monsoon flows over the Indian subcontinent. The India-wide monsoon has been linked to a 13% rainfall deficit, making Kolkata’s local weather pattern a marked departure from the broader trend.
The Regional Meteorological Centre attributed the difference to the regular formation of low-pressure areas and other systems over the Bay of Bengal. The most recent system, a deep depression, brought five consecutive days of rain to the city and surrounding areas.
Biswas said Bengal would remain outside the zone of influence of a depression affecting parts of Myanmar and northeast India. Kolkata is expected to see mostly dry weather over the next few days, with only scattered or isolated rain possible. The southwest monsoon normally withdraws from the region between the first and second week of October, while withdrawal has already begun in parts of northwest India.
