The Met office on Sunday said the city and its adjoining areas are expected to receive more rain during the next few days as the monsoon in south Bengal has become active for the first time this year, ever since it entered the region on June 6.

?The monsoon flow over south Bengal, which was earlier weak, has now become active. So, Calcutta and the districts of south Bengal are expected to receive more rain during the next few days,? said G.C. Debnath, director of the weather section at the Regional Meteorological Centre in Alipore.

Officials said the monsoon was more active in north Bengal over the past two days. ?We have issued a warning for heavy rain in the north Bengal districts for the next 24 hours. Pockets of Jalpaiguri have received 100 mm of rain over the past 24 hours. In the next few days, the south Bengal districts, including Calcutta, will receive more rain,? an officer said.

One of the factors that helped build up the monsoon current over Calcutta is a trough of low pressure that stretches from east Madhya Pradesh to Meghalaya across central Bengal. ?This trough of low pressure is among various other atmospheric factors that strengthened the monsoon current over the city and its adjoining areas,? an officer said.

Officers at the Met office on Sunday said the signs of the monsoon strengthening have been evident since Friday evening, when the wind speed began to rise.