Monsoon made a meek entry in Calcutta on Friday.

This was among the driest arrivals of the southwest monsoon in the city in the past few years. The Met office recorded 1.6mm of rain between 8.30pm in Alipore between Thursday night and Friday night.

The monsoon currents are weak, and there is no system on the Bay that can trigger heavy rain in the city for at least the next couple of days, Met officials said.

“The southwest monsoon has further advanced into the entire northwest Bay of Bengal, some more parts of the westcentral Bay of Bengal, most parts of Bengal, some more parts of Bihar, and some parts of Odisha and Jharkhand, today. The northern limit of monsoon passes through Purulia in Bengal and Dhanbad and Muzaffarpur in Bihar,” said a Met bulletin.

The usual date of monsoon’s onset is June 5 in north Bengal and June 10 in south Bengal. This year, monsoon set foot in north Bengal on June 8.

A Bay system often propels monsoon before time into mainland. The onset, if it coincides with a strong Bay system, is marked by formidable rain.

Last year, the monsoon arrived in south Bengal on June 17. The city received around 23mm of rain. A cyclonic circulation was active over the northwest Bay of Bengal.

In the absence of any such system, the arrival in Calcutta was lacklustre.

Even if brief, the precipitation looked more like monsoon rain and thundershowers. There was hardly any breeze.

As the days progress, the nature of the rain will change, said the weatherman. The stormy showers, along with streaks of lightning, will be replaced by uniform and persistent rain, he said.

In south Bengal, Hooghly, East Midnapore and Purulia received more rain than the rest. In the coming days, light to moderate rain is expected across south Bengal over the next three to four days.

North Bengal is likely to get heavy rain, according to the Met forecast.

On Saturday, thunderstorms are expected in Jhargram, Purulia, West Midnapore, East Burdwan and West Burdwan.