Calcutta has run up a 40 per cent rain deficit this monsoon and the shortfall is unlikely to reduce over the next four or five days as the weather department has ruled out heavy showers during the period.

"The cyclonic circulation that brought downpour to parts of the city on Friday is shifting north, so there is little chance of heavy showers over the next four or five days," a weather department official said. "The city may, however, get short spells of showers because the moisture-laden wind is blowing from the direction of the Bay of Bengal."

From June 1 to July 17, Calcutta has received 301mm of rainfall; the normal for this period is 502.8mm. The deficit stands at 40.14 per cent.

"So far this monsoon, rainfall has been deficient in south Bengal, especially in Calcutta, Howrah, Hooghly and East Midnapore. The situation is favourable for heavy rain in north Bengal," said G.C. Debnath, deputy director, India Meteorological Department, Calcutta.

Between July 1 and 17, the city has recorded 169mm of rainfall, much lower than the 396.6mm recorded in the same period last year and the 277.8mm recorded in 2014. July has traditionally been the rainiest month in Calcutta, bringing on an average 399.9 mm of rain.

"The cyclonic circulation, which is heading north, is pulling the trough of low pressure away from Calcutta. That system will remain active for at least the next four or five days. The two systems will draw moisture away from Calcutta, reducing the cloud cover and rain," Debnath said.

Thunderclouds might still develop because of heat and humidity in the atmosphere, bringing short spells of rain. "That rain, however, will not be enough to make up for the deficit," a weather expert said.

The low-pressure trough is an imaginary line joining various low-pressure points across the breadth of the country. During the monsoon, the places that fall on or near the trough get intense rainfall.

Not just Calcutta, the entire east and Northeast India have been facing rain deficit - 23 per cent. The IMD in its long-term forecast has said the monsoon will be normal in India this year. For that to happen, more rain is needed in the second half of the monsoon in the east and Northeast India.

"We expect rainfall in Calcutta and its surrounding areas to pick up in August. Before that there is little chance of heavy rain in the city," Debnath said.

The maximum temperature, which was around 30 degrees Celsius over the past couple of days, is likely to rise to 32-33 degrees, slightly above the normal mark.