Calcutta, Oct. 10: A third weather system has developed over the Bay of Bengal in as many days, dampening the festive spirit on Navami and threatening to pour more misery as the city prepares to bid the goddess a fond farewell.

The cyclonic circulation was positioned northwest over the Bay of Bengal on Monday, covering adjoining parts of the state and Odisha. This is what triggered the rainfall in most parts of Calcutta almost the entire evening, the weather office said.

More rain has been forecast for the city and its surrounding areas on Tuesday and Wednesday, which would be worrying for Puja organisers planning to immerse their idols on Dashami.

How much rain the cyclonic circulation, the second in a week, would bring is hard to predict, said G.K. Das, director of the India Meteorological Department (IMD), Calcutta. "The skies might open up at any time of day or night over the next two days."

The cyclonic circulation is tipped to cause "heavy rain" in neighbouring North and South 24-Parganas and East and West Midnapore on Dashami. In Met parlance, heavy rain is 60 to 120mm in 24 hours.

A cyclonic circulation that had developed over the Bay of Bengal last week was the original cause of worry. That system has since moved away, only for a new threat to emerge on Navami.

The first cyclonic circulation made landfall in Odisha on Saptami (Saturday) morning and has since shifted to Jharkhand. According to the weather office, it is now too far away from Calcutta to affect the local weather significantly.

By the time the original cyclonic circulation had weakened on Sunday, a low-pressure trough formed in eastern India, stretching from Bihar to Odisha. The weather office said it might have the same effect as the cyclonic circulation, causing rain on Navami and Dashami not only during the day - as had happened on Saptami and Ashtami - but also in the evening.

The low-pressure trough dissipated on Monday, but the new cyclonic circulation has put a question mark on hopes for a rain-free end to the Durga Puja festivities.

The cyclonic circulation and the residual effect of the earlier system were what caused rain in parts of the city on Monday morning. The longer and heavier spells of rain were in the evening. The volume and distribution of rainfall was uneven.

According to data recorded by the Calcutta Municipal Corporation, the Belgachhia-Shyambazar area received about 2.5mm of rain between 5pm and 6pm. The Behala CPT canal area got 10 times as much rain over the same period. Ballygunge received about 9mm. Kidderpore, Kasba and Dum Dum are some of the areas that received heavy rain in the evening, resulting in waterlogging on several roads.

The rain effect was instantly felt at pandals across the city. Three-year-old Bhargoo Saha wore a raincoat as he headed towards the Ekdalia Evergreen pandal on his father's lap around 6pm. The Sahas of Dum Dum were determined not to let the weather forecast curtail the last full day of pandal-hopping.

Bhargoo's father Ajay said the skies opened up when he and his family were visiting Deshapriya Park. "The forecast had predicted rainfall; so we came with an umbrella each. For my son, we had a raincoat ready."

Around the same time, the rainfall was heavier in Salt Lake.

Lake Town residents Rohini Chakraborty, 28, and Prajwal Sarkar, 29, were clicking selfies at the FD Block pandal when it started pouring, forcing them to run into a food stall. "We aren't carrying umbrellas and I hope it stops raining soon, otherwise we will miss most of the pandals in north Calcutta," rued Rohini.

At Telengabagan, elderly couple Shatadipa and Debabrata Bandyopadhay sought refuge in a bus-stop shed. "The weather office had predicted rain. We should have brought along our umbrellas," Debabrata said.