Alipore: The mercury is on its way up in Calcutta after Sunday's thunderstorm, heralding a warm phase. The weather on Tuesday felt like 40 degrees Celsius though the actual temperature was much less.

The weather department expects the condition to further worsen over the next two days as there is little possibility of thunderstorms that can bring some relief - albeit temporary - from the sweltering heat.

The maximum temperature in Calcutta on Tuesday was 33.5 degrees Celsius, one degree below normal. The RealFeel temperature calculated by weather portal Accuweather.com was as high 40 degrees Celsius at 1pm because of high humidity.

The RealFeel - which is calculated taking into account various weather parameters such as temperature, humidity, wind speed and direction and the angle of the sun - is likely to be even more on Wednesday and Thursday.

According to the weather department, the maximum temperature on the two days is likely to be in the region of 35 degrees Celsius but the relative humidity is likely to fall a little.

The change in weather conditions between Monday and Tuesday was stark, which is why people felt even more uncomfortable.

"Both the maximum and minimum temperatures on Monday were the lowest in Calcutta in the last one-and-a-half months. Both readings were five notches below normal. But as the sun came out strong in the city on Tuesday and the moisture content in the air shot up, conditions became uncomfortable," said a senior Met official.

"A higher saturation of moisture did not make conditions sweaty on Monday because there was hardly any sunlight coming through, which is why the maximum temperature stayed low at 30.4 degrees Celsius. But with the sun coming out on Tuesday, the discomfort level shot up," said G.K. Das, director, India Meteorological Department, Calcutta.

When the temperature rises, the body sweats to lose heat. As sweat evaporates from the skin, it leaves behind a cool feeling.

When the moisture content in the air or relative humidity is high, the sweat does not evaporate easily. The sweat lingers on the skin, causing a sticky and uncomfortable feeling.

The moisture was being brought in by a south-westerly wind blowing from the Bay of Bengal into Calcutta and its surroundings.

"But now a north-westerly wind has started to blow. It will be the dominant wind in the region over the next couple of days," a Met expert said.

Under the impact of the dry, north-westerly wind, the moisture content in the air will come down but the temperature will rise. "So, the feeling of discomfort will still be there," the expert said.

According to Das, the dry north-westerly wind would also reduce the chances of rainfall in the city on Wednesday and Thursday.

"A trough of low pressure that was facilitating the moisture incursion from Bay has moved away. A new weather system, a cyclonic circulation, has formed over Jharkhand but it is 2.1km above the surface, and hence not very effective," he said.