Calcutta, Oct. 22: If you spent the Saturday evening cooped up in your home, blame it on a leech-like phenomenon that turned voracious overnight, sucked moisture and ballooned so big that the entire eastern coast came under its rain-spewing spell.

It has fed on enough moisture to hold out the threat of rain for another 48 hours, weather officials said.

The low pressure over Calcutta ? the reason behind the relentless rain over the last four days ? did weaken and dissipate on Saturday as the Met office predicted.

But no one foresaw the change in behaviour of another trough of low pressure that has been hovering over the Northeast for the past three days.

In the early hours of Saturday, the trough shed its benign character and started expanding, travelling all along the coast and stretching right up to Tamil Nadu, all the time sucking in moisture from the sea.

The upshot: for the fifth successive day, Calcutta and the districts continued to be battered by rain. Residents of several areas in the city have been trapped indoors, keeping them away from both work and shops. The artisans of Kumartuli, racing against the Kali Puja deadline, have been hit hard.

The impact of the rain is also telling on the flow of fresh supplies to markets. A shortage of vegetables and a consequent price spurt are feared.

Unless there is a dramatic change, the weather is unlikely to improve on Sunday, Met officials said.

“We expect plenty of rains tomorrow. Subsequently, the intensity of rains may reduce on Monday but the sky is likely to remain cloudy with more rains. Overall, the situation is not very hopeful during the next two days,” said G.C. Debnath, the director of weather section at the Regional Meteorological Centre at Alipore.

The formation of a cyclonic (anti-clockwise movement) upper air circulation over Jharkhand and its neighbourhood has worsened the situation.

“Under the combined effect of the low pressure trough and the upper air circulation, the heavy incursion of moisture into Bengal is not stopping,” he added.

Debnath said that heavy rainfall is expected at a few places in the state during the next 24 hours. Heavy to very heavy rain is expected in North Bengal during the next 48 hours.

In the districts, especially in Midnapore, the flood situation has worsened and four deaths have been reported from different parts of the state.

“Eight lakh people have been affected. Though the situation is not alarming, it is certainly grave,” state finance minister Asim Dasgupta said after a visit to some flood-affected areas.