A hailstorm described by locals as the worst in living memory has smashed a Victorian town, damaging cars and homes and forcing businesses to shut.

Giant hail and torrential rain from a severe thunderstorm pummelled Casterton, a historic town in western Victoria, on Wednesday afternoon.

The Severe Weather Victoria Facebook page described “unreal scenes” as the supercell caused flooding, landslides, ice-covered roads and destruction of homes and vehicles.

“Never seen anything like,” it wrote.

The main street of Casterton, a rural town on the Glenelg River. Photo: Facebook/Casterton News

Higgins Storm Chasing said damaging to destructive winds tore roofs off some houses.

There was “plenty of damage” with “hail up to tennis ball size” smashing windows and car windscreens.

Residents also reported house fires breaking out due to the damage.

Cars and homes were slammed by hail. Photo: Facebook

The local State Emergency Service and Country Fire Authority received more than 70 calls for help.

“It was just like the heavens let loose. To be honest, it was pretty wild,” one resident told Nine’s Today show.

“My mum’s car got smashed up pretty bad. A lot of stores in town got a couple of roofs, ceilings fell.”

A huge clean-up operation will be in full swing on Thursday as the town surveys the mayhem.

Hail the size of golf balls – and tennis balls – were reported. Photo: Facebook/Aishwarya Rani

It comes as severe thunderstorms and damaging winds are predicted to  affect Australia over the next three days, impacting at least five states and territories.

Ngảire Gilberd-Roberts said people in Casterton were “horrified” at the amount of devastation.

“Hail stones the size of golf balls, breaking windows, and leaving the township in disarray.

“Cars deeply pitted, broken windscreens, wing mirrors damaged, and the whole town is horrified at the amount of devastation.

A combination of flooding and hail created havoc. Photo: Facebook (Casterton News)

Gilberd-Roberts said Thursday would be a “massive clean-up day”.

“The trees that line Henty Street have suffered immensely losing much of their beautiful spring foliage,” she said.

“The hail was so heavy that it was piled up at least six inches (15 centimetres) for a few hours after the storm had passed.”

Local shops, restaurants, motor mechanics and other businesses took to Facebook to advise they would be closed after their shops were hit.

A thick carpet of hail pebbles. Photo: Facebook/Taylor Hogan

Coffee shop Grab n Go said it would be closed until further notice after the “apocalypse that we have encountered today”.

“Let’s all band together and help out our fellow traders and just bare in mind that a lot of us have lost a lot so just be patient and understanding and help where you can.

“Everyone will need your support when we get up and running so please support local business and let’s keep Casterton going.”

Storms spread

Weatherzone said on Wednesday there would be “prolific storm activity” across the southern half of Australia in the coming 72 hours.

On Thursday, showers and dangerous thunderstorms would spread across South Australia and parts of Victoria, NSW and the Northern Territory.

“This is likely to involve severe storms in multiple states, with damaging to destructive winds, large hail and bursts of heavy rain all a risk,” the forecaster said.

“A surge of powerful winds will also sweep across South Australia on Thursday, with damaging winds likely to develop over the state’s north and west.”

On Friday, rain and thunderstorms would continue to spread across southeastern and eastern Australia.

“Parts of NSW, Victoria, the ACT, Tasmania and Queensland will be affected by wet and stormy weather on Friday, with severe storms likely in most of these states,” Weatherzone said.

“The set-up on Friday will be conducive to multicell thunderstorms and squall lines, and possibly supercells.

“These types of storms increase the risk of destructive winds and very large hail.”