The long-awaited monsoon is at long last in Calcutta, the Met office said on a day the city was bone dry in most parts.

The sky, consistently cloudy on Friday, bore the stamp of the monsoon.

“Those were typical monsoon clouds, coming from the Bay of Bengal,” said a Met official.

The rain that happened the day before and the change in the wind pattern prompted the Met office to announce the onset of the monsoon.

“We take the rain in the past 24 hours into account. Between 8.30am on Thursday and 8.30am on Friday, most parts of Calcutta received rain. Alipore got around 5.5mm,” said H.R. Biswas, head of the weather section at the Regional Meteorological Centre, Calcutta.

Parts of the city received drizzles later, too.

A Met bulletin issued on Friday afternoon said: “Southwest monsoon has further advanced into remaining parts of north Bengal and also some parts of South Bengal today... it covered all districts of north Bengal and North 24-Parganas, Nadia, Kolkata, most parts of South 24-Parganas, Murshidabad and some parts of East Midnapore, Howrah, Hooghly, East Burdwan and Birbhum districts of south Bengal.”

Nadia’s Swarupnagar got more than 65mm of rain in the same period.

The disparity in rainfall on Monday was attributed to the absence of a system over the Bay of Bengal.

“If a low-pressure area over the Bay propels the monsoon into Calcutta, the rain is uniform and widespread,” said a weather scientist.

This year, the monsoon arrived in Calcutta late. The usual date of its arrival is June 10. Cyclone Remal had propelled the monsoon currents into north Bengal on May 31, ahead of its June 5 schedule.

The northern limitof the monsoon nowpasses through Haldiain East Midnapore, thebulletin said.

“Conditions are favourable for further advance of southwest monsoon into some more parts of Odisha, south Bengal, Jharkhand and Bihar during thenext 3-4 days,” the bulletin said.

An east-west trough now runs from northeast Rajasthan to Manipur across Uttar Pradesh, Bihar, north Bengal, Bangladesh, Meghalaya and Assam, the Met bulletin on Friday said.

A cyclonic circulation lies over Bihar and adjoining East Uttar Pradesh, the Met bulletin added.

“The trough needs to descend to cause more rain in Calcutta and adjoining areas,” said Biswas.

But the clouds that covered the sky were a pointer to the onset of the monsoon, he said.

The city is likely to get light rain on Saturday.