As cyclone 'Sitrang' moved north-northeastwards and lay 260 km southeast of Sagar island on Monday, the Met department warned of heavy rain in coastal Bengal and northeastern states, dampening festive spirits on Diwali and Kali Puja.

Intermittent showers since morning forced people to remain indoors as most Kolkata streets wore a deserted look on a festive evening which would normally have attracted tens of thousands to visit marquees with idols of Goddess Kali and see the bright lights of the city.

Squally wind accompanied by light to moderate rain affected the coastal districts of the state, while Kolkata also witnessed an overcast sky with light precipitation.

Moving at a speed of 33 kmph in a north-northeastward direction, cyclone 'Sitrang' lay 260 kmph southeast of Sagar island at 2.30 pm over the northwest Bay of Bengal and is very likely to intensify further into a severe cyclonic storm, packing wind speed of 90 to 100 kmph, gusting to 110 kmph by Monday night.

It is likely to cross the Bangladesh coast between Tinkona island and Sandwip near Barisal early on Tuesday, the weather office said.

The system will cause heavy to very heavy rain in districts of South 24 Parganas, North 24 Parganas, Purba Medinipur and adjoining areas of Paschim Medinipur in south Bengal on Monday, the Met said.

It will also cause a downpour on Tuesday in North 24 Parganas, South 24 Parganas and Nadia districts.

The weather system is also likely to bring in "heavy to extremely heavy rain in south Assam, Tripura, Meghalaya and Mizoram and heavy to very heavy rain in north Assam, Arunachal Pradesh, Nagaland and Manipur on Monday", the Met said.

Heavy to very heavy rain will occur on Tuesday in Arunachal Pradesh, Assam, Meghalaya, Mizoram and Tripura, the meteorological department said.

Diwali and Kali Puja celebrations were partially affected in south Bengal owing to the inclement weather.

However, despite bad weather, devotees turned up in droves since early morning at popular Kali temples like Kalighat, Dakshineswar, Thanthania and Lake Kalibari in Kolkata.

Kali Puja is celebrated in the state, particularly in North 24 Parganas district where it is considered the biggest festival, by community puja organisers, in many temples as well as in numerous households.

The weather office said the main affected areas by the cyclone will be the Sundarbans in the coastal areas of North and South 24 Parganas districts of West Bengal and in Bangladesh.

Heavy rain accompanied by high wind, gusting up to 100 kmph, and high tidal waves are likely to cause damage to kutcha (mud) embankments and roads, disruption of power supplies and communication, it said.

The deputy director general of the regional meteorological centre here, Sanjib Bandopadhyay, has said that the breach of kutcha embankments, owing to the storm surge accompanied by a high astronomical tide on the new moon, may lead to seawater inundation of low-lying areas.

Tidal waves are likely to reach a height of six metres owing to the twin effect of the weather system and astronomical tide.

A Kolkata Municipal Corporation official said steps are being taken to tackle any situation that may emerge in the metropolis owing to 'Sitrang'.

The weather office warned that wind speed over sea areas will reach a speed of 90 to 100 kmph, gusting to 110 kmph, in the north Bay of Bengal, and advised fishermen not to venture into the sea and suspension of all offshore activities during October 24 and 25.

Ferry services in Sunderbans and water-bound tourist activities at seaside resort towns of Digha, Mandarmoni, Shankarpur, Bakkhali and Sagar have been stopped on October 24 and 25 as a precautionary measure.