A drop of nearly two notches from Wednesday's temperature failed to bring relief from the searing heat on Thursday as the minimum relative humidity soared from 43 per cent to 51 per cent, making it feel like 51 degrees at noon.

The RealFeel temperature is the effect of temperature, relative humidity, wind and the angle of the sun on the human skin.

The increased humidity during the day was the result of excess moisture being fed into land by two cyclonic circulations that had formed over the Bay of Bengal.

As a result, the daytime relative humidity reached the 60-75 per cent band and made the weather extremely uncomfortable as the sweat stayed on the skin.

Noon was the most uncomfortable on Thursday when the temperature and humidity were both high at 35 degrees Celsius and 64 per cent, taking the RealFeel to 51 degrees Celsius. Later in the afternoon, it hovered between 46 and 50 degrees Celsius as the temperature came down to 33 degrees Celsius but the humidity increased to 75 per cent.

But there is hope of relief from Friday as the cyclonic circulations are likely to lead to cloud formation and shade the city from the sun's rays. The temperature is expected to come down and the feeling of discomfort, too, would diminish, the weatherman predicted on Thursday.

Rainfall is expected in parts of south Bengal, including Calcutta, which has not received any shower for the past five days except for a few drops on Thursday.

"At present, there are two cyclonic circulations around Calcutta," said Gokul Chandra Debnath, deputy director general of meteorology, IMD, Calcutta. "One over Bangladesh adjoining the Bay and another near Andhra Pradesh adjoining the Bay. Clouding and rainfall is expected in south Bengal because of these circulations."

As cyclonic circulations have atmospheric pressure lower than their surroundings, they pull air towards themselves. In this case, it is pulling moisture-laden air from the sea towards land. This would lead to clouding and the temperature was unlikely to be more than 33 degrees Celsius on Friday, a Met official said. The RealFeel temperature is likely to come down as well.