Update: The SES received 200 calls for help within two hours as Melbourne's north was hit by what was believed to be a tornado on Thursday afternoon.

Bureau of Meteorology duty forecaster Michael Efron said the tornado struck the outer northern suburbs of Tullamarine, Craigieburn, Campbellfield  between 1.30pm and 2pm.

The weather bureau as of 3.15pm revoked its tornado warning for Melbourne, and the twister that was sighted in the northern suburbs had reportedly dissipated.

From about 4pm, heavy rain was pelting Koo Wee Rup and Bunyip as the wild weather moved towards south Gippsland.

BOM duty forecaster Steven McGibbony said the storm extended an area of approximately 30km.

"The more intense part of the storm is just south-east of Koo Wee Rup and Bunyip," Mr McGibbony said.

"We have removed the mention of large hail from the storm. The storm does not look tall enough to be producing large hail but we are still warning for damaging wind and heavy rainfall."

Mr McGibbony said there had not been any reports of damage associated with the tornado.

"If it has touched down somewhere, it has only been very briefly and only where there were no houses," he said.

The Bureau could not verify if photos circulating on social media were of the tornado but said the weather radar showed conditions could have formed a twister, which led to the warning.

And Mr Efron said the risk of showers in the city centre still remained for later today.

"There is relatively dry conditions at the moment in Melbourne, but further showers are expected ...later this afternoon," he said.

"There will be more showers moving in from the north in a couple of hours.

"We have had reports of flash flooding across the Melbourne CBD and inner-western and northern suburbs."

The last confirmed tornado sighting in Melbourne was in Keilor Downs, 20 kilometres north-west of the CBD, on Christmas Day in 2011.

"We had some volunteers there and they had to run for shelter," a SES spokesman said at the time.

The Bureau of Meteorology had warned that at 1:50 pm on Thursday, very dangerous thunderstorms were detected on the weather radar near Bulla.

The State Emergency Service advised people to keep clear of fallen power lines; secure any loose objects in the vicinity of your home, and switch off your computer and electrical appliances

Earlier, heavy rain drenched Victoria, with some parts of the state experiencing their wettest November day in more than 100 years.

More than 20 millimetres of rain fell across Melbourne on Thursday morning, drenching commuters, Oaks Day racegoers and shoppers waiting to snap up H&M's latest fashion range

with Patrick Hatch

Bit of rain about! #melbourne #melbweather #storm pic.twitter.com/awbICv6P95— Scott Carne (@SMCarne) November 5, 2015

Can't really tell, but this is the biggest storm I've seen since I've been in melbourne pic.twitter.com/pXeBDdRrdu— Matt (@tradermatt106) November 5, 2015

#LittleBourkeStreet #Melbourne has turned into a river, photo taken by Mezzo Melbourne at entrance to #AmphlettLane pic.twitter.com/Xjeue2DbkE— Amphlett Lane (@AmphlettLane) November 5, 2015

It still stands! These pics were taken ten minutes apart #Melbourne @abcnewsMelb @abcnews pic.twitter.com/8CbYpohKPG— Ben Lisson (@BenLisson) November 5, 2015

Glad I didn't ride my bike today.... #melbourneweather pic.twitter.com/Ogjz7mEcnD— Luke Gamon (@lgamon) November 5, 2015