Melbourne mops up after record hailstorm

A once-in-a-century storm caused major flooding in Melbourne. Photo / Getty Images

Interstate reinforcements have been called in to help mop up after a once-in-a-century "beast" of a hailstorm battered Melbourne.

And the city is bracing for more wild weather, with Victorians warned to batten down the hatches over the coming 24 hours.

Eighty State Emergency Service (SES) volunteers have been sent from NSW and South Australia as Melbourne counts the cost of the fierce Saturday storm that flooded roads and buildings and left thousands of people in the CBD stranded.

The SES received 4200 calls for help until midday Sunday and more are expected as conditions deteriorate and holiday-makers return from the Labor Day long weekend.

Eleven families in Melbourne have had to be relocated, together with four from Warrigal and Traralgon in Gippsland.

At the height of the emergency, power was cut to 100,000 homes, and 100 traffic lights were disabled, causing traffic chaos.

Bureau of Meteorology forecaster Kevin Parkin said the storm brought hailstones the size of lemons in an event perhaps not seen since early last century.

"The weather system that brought the damage to Melbourne is known in meteorological terms as a supercell thunderstorm, an organised beast of a storm that once it gets going tends to last more than your average thunderstorm," he said.

Another storm front was expected to hit later on Sunday before the state would be "belted" with wind gusts of up to 100km/h on Monday.

Victorian Premier John Brumby warned people to be careful outdoors, particularity in bushfire areas where trees had become weak and unstable.

"There have been no reported fatalities or serious injuries. For that we are grateful," he said.

"People really should take great care as we move through this afternoon, tonight and into tomorrow and make sure we put this focus on protecting life and protecting public safety because all the advice is that it will be a pretty difficult period."

The insurance industry has opened 24-hour hotlines for people affected by the storms.

There is no official estimate of the damage bill, which is expected to rise when holiday-makers return home.

Mr Brumby said eight police stations and 20 schools had been damaged, while surgery had been disrupted at The Alfred hospital because of flooding.

Melbourne's major train hub, Southern Cross Station, had its roof punctured by the hail and the National Gallery of Victoria was also flooded.

The emergency services dispatch centre received 600 calls for help every half hour between 3pm and 7pm (AEDT) Sunday, while 500 SES volunteers were mobilised.

The worst-hit area was Knox, in Melbourne's southeast, where the SES responded to 1600 calls.

Authorities have urged the public to only contact the SES in an emergency.

- AAP