A sultry weekend has set the stage for a hotter week ahead, Sunday afternoon's 35.6 degrees Celsius feeling more oppressive than it should have because of a combination of weather systems that triggered a spike in humidity.

The maximum temperature is tipped to rise further on Monday and hit around 38 degrees Celsius by Wednesday. The flip side of the forecast is that the current weather conditions are ideal for a series of thunderstorms to originate in Jharkhand and the western districts of Bengal.

If these clouds pass over the city, there is a chance of a shower accompanied by cool winds. A tempest strong enough to fell trees and tear down billboards is also a possibility, weather scientists said.

Saturday had been hot and humid too but the appearance of two cyclonic systems on either side of the city made the Sunday weather worse. The two systems triggered heavy incursion of moisture from sea to land, making the air sticky.

"There is a cyclonic circulation above Bangladesh and another one over north Chhattisgarh. As these systems have atmospheric pressure lesser than their surroundings, they have been pulling in water vapour from the sea," a senior official of the Met department said.

Sunday was especially uncomfortable because both the maximum temperature and the minimum relative humidity, which represents the moisture content in the air during the hottest part of the afternoon, shot up overnight.

The day's maximum temperature was a degree above normal and 1.4 degrees more than Saturday's reading. Minimum relative humidity rose to 61 per cent, four per cent more than the previous day.

"I went to have lunch with a friend in Ballygunge on Sunday and had to wait about 10 minutes for him after parking my car. I sweated so much during that time that my handkerchief got soaked," said Arpan Roy, a 34-year-old businessman from Jodhpur Park.

Sweating is the body's mechanism of cooling down. The sweat evaporates easily when relative humidity is low but perspiration tends to linger on the skin when it is high.

According to AccuWeather.com, the RealFeel temperature in the city was 51 degrees Celsius at 3pm on Sunday. RealFeel temperature is calculated taking into consideration multiple weather parameters such as temperature, humidity, wind and the sun's angle.

Thunderclouds have been forming in the state over the past couple of days. The storm on Saturday night was classified as a squall because it hit town at a speed of 58kmph and maintained that intensity for two minutes.

The formation of thunderclouds, however, doesn't guarantee storm and/or rain everywhere in the region because these clouds are more tall than wide and generate storms that affect only the narrow path through which they travel.

On Saturday, two such clusters of clouds brought rain to Calcutta in phases. The clouds fizzled out on Sunday. "There can be many reasons why thunderclouds fizzle out or become stronger as they move. Some of the factors are the presence of moisture in the air along the way and also the direction of the wind. These factors were not favourable for the clouds to travel over Calcutta," a weather scientist said.