The mercury almost touched 40 degrees Celsius in the northern tip of Calcutta on Friday, and the Met office warned of hotter days ahead.

The maximum temperature at Dum Dum was 39.4 degrees on Friday, the Met reading said. In Alipore, the official record keeper for Calcutta, the maximum temperature was 38.6 degrees, making Friday the hottest day of the season so far.

To make things worse, the air had just enough moisture to make the conditions extremely uncomfortable. Around 2pm, a private agency showed the weather in Calcutta was 38 degrees. The RealFeel was 44 degrees.

“Dry westerly and northwesterly winds are dominating south Bengal, pushing the Celsius up. The coastal districts still have some moisture near the surface, making the conditions sweaty and uncomfortable,” said a Met official.

The Met office has already predicted a heatwave in south Bengal from May 10 and in north Bengal from May 11. It is expected to last for a couple of days at least. In Calcutta, the Celsius is likely to go up a notch, said the official.

A heatwave is declared when the mercury breaches the 40-degree mark and the maximum is five notches above normal. Last year, April saw multiple heatwaves in south Bengal, including Calcutta.

The maximum temperature had breached the 40-degree mark in the city more than once. Compared to that, April had been mild in the city. The first few days of May were also bearable.

The mercury has already breached the 40-degree mark in the districts. Kalaikunda in West Midnapore was among the hottest places in the state on Friday, sizzling at 42.3degrees.

A tour around the city showed several glimpses of assault of heat and humidity. In the afternoon, two in three pedestrians were seen either under umbrellas or with their faces covered or both.

A Met bulletin said West Burdwan, Birbhum, Purulia, Bankura, Jhargram and West Midnapore were among the districts likely to bear the maximum brunt of the heatwave.

The humidity will also be formidable, especially in the coastal districts.

“Day temperature is likely to rise by 2-3°C over the next two days. It is expected to be above normal by 3-5°C over south Bengal from May 10.The maximum relative humidity over coastal districts is likely to be between 80and 90 per cent. In the interior districts, it is likely to be in the range of 70 and 80 percent. The minimum relative humidity is likely to be 45 -55 per cent over coastal districts and 30-40 per cent over interior districts,” the Met bulletin said.

It has also predicted some relief in the form of “isolated thunderstorms” in the coastal area and in north Bengal on Sunday and Monday.

“If the thunderclouds are over North and South 24-Parganas, then parts of Calcutta may also get some rain,” said the Met official.