Kolkata, 11 August (H.S.) : Kolkata witnessed another spell of exceptionally heavy rain on Monday evening, with Belgharia recording as much as 130 mm of rainfall within an hour as rapidly developing thunderclouds triggered a sudden change in weather conditions across parts of the city and neighbouring districts.

After enduring intense sunshine and humid conditions throughout the day, Kolkata residents were caught off guard as the weather changed dramatically after sunset. The episode brought back memories of the torrential rain that paralysed the city on September 23, 2025, when Kolkata recorded 251.4 mm of rainfall within 24 hours. Of this, 185 mm was recorded between 2:30 am and 5 am, while around 100 mm fell within a single hour.

In meteorological terminology, rainfall of 100 mm or more within an hour is classified as an extremely intense rainfall event and is commonly described as a cloudburst. Monday evening's rainfall once again produced conditions comparable to those witnessed during the September 2025 episode in several parts of the city.

The weather changed rapidly on Monday evening following a day of oppressive heat and humidity. Cumulonimbus clouds began developing over Kolkata and adjoining areas, with thick cloud formations spreading rapidly across the skies over parts of Howrah, North 24 Parganas and Hooghly.

Rain began at around 6:30 pm and intensified sharply within a short period. The central and northern parts of Kolkata experienced particularly dense and vertically developed cloud formations, resulting in exceptionally heavy rainfall over a relatively small area.

Belgharia recorded 130 mm of rain in just one hour, while the Thanthania Kalibari area received around 100 mm during the same period. Ultadanga and Dattabagan also recorded close to 100 mm. Rainfall of around 90 mm was recorded at Birpara, while Maniktala received approximately 80 mm in an hour.

The intensity of the downpour quickly inundated several areas, including Muraripukur, Ultadanga, Shyambazar, Ahiritola, Tala, Belgharia and Deshbandhu Park. Roads were submerged within a short time, causing significant disruption for commuters returning home from work during the evening.

The sudden downpour came after a relatively brief lull in rainfall. Kolkata had experienced rain for five consecutive days between August 2 and August 7, while Saturday and Sunday passed with little or no significant rainfall in the city. Most parts of South Bengal also remained comparatively dry during the weekend, leading to an initial assessment that the active spell of rain had temporarily weakened.

Monday evening's intense rainfall, however, challenged that assessment.

The latest forecast issued by the Alipore Meteorological Office on Tuesday morning indicated that the cloud cover was not widespread across the state. Instead, concentrated cloud formations were primarily observed over Kolkata and parts of Howrah, Hooghly and North 24 Parganas.

This suggests that Monday's extreme rainfall was largely a localised phenomenon caused by the rapid development and intensification of thunderclouds over a relatively limited area, rather than a widespread rain system affecting the entire state.

Weather patterns observed in recent years indicate that such rapid cloud development has become a recurring feature during the monsoon season. The cloud formations during Monday's episode are estimated to have reached heights of around 12 to 13 kilometres.

Similar intense cloud-development events have already been observed three times in June, twice in July and once in August before Monday's episode this year.

The latest spell once again highlights Kolkata's vulnerability to short-duration, extremely heavy rainfall, in which a large volume of rain can fall within a very short period and rapidly overwhelm roads and drainage infrastructure even when surrounding areas receive considerably less rainfall.

Hindusthan Samachar / Satya Prakash Singh