The wait for the monsoon just got longer.

The monsoon is likely to arrive in south Bengal after June 20, a Met official said on Sunday.

Hot and humid conditions are likely to torment Calcuttans for a little longer, according to the forecast.

A couple of days ago, the Met office had said that the southwest monsoon was expected to enter south Bengal around June 18-19.

“The change in the wind pattern that is expected to propel the monsoon into south Bengal is slower than expected. Southerly winds are important for the arrival of the monsoon,” said the official.

“Southerly winds are there in the lower level of the atmosphere in south Bengal. But westerly winds are still dominant in the mid-level atmosphere. The westerly component has to weaken for the monsoon currents to enter south Bengal,” the official said.

A Met bulletin issued on Sunday said as much.

“The northern limit of monsoon continues to pass through Islampur (North Dinajpur). Conditions are favourable for further advance of southwest monsoon into some parts of South Bengal and remaining parts of North Bengal during next 4-5 days,” the bulletin said.

“Heat wave along with hot and humid weather conditions are likely to prevail in the western districts of south Bengal during the next two days. Rain/Thunderstorms and associated weather activity are likely to occur at a few places over the districts of south Bengal.”

Purulia, West Burdwan and West Midnapore are likely to reel under a heat wave on Monday as well. “Hot and humid weather conditions are likely over Jhargram, Bankura and Birbhum districts,” the bulletin said.

While the western districts of Bengal are likely to get scattered rainfall in the next couple of days, Calcutta can expect “isolated” showers.

Thunderstorms with lightning and gusty wind are likely in south Bengal on Monday and Tuesday.

The rainfall spread and intensity are likely to go up marginally from Wednesday.

Calcutta suffered another pressure cooker-like day on Sunday. At 36.4 degrees, the maximum temperature was a couple of notches above normal. But it felt like 45 degrees because of high humidity.

This year, the monsoon arrived in north Bengal on May 31, ahead of its usual onset date of June 5.

For south Bengal, the usual arrival date is June 10.