The worst of an intense superstorm that left an entire state without power is far from over with warnings that more wild weather is on the way.

The Bureau of Meteorology said the once in 50-year storm would move through the south coast of Australia in the next 24 hours and will cause more havoc across southeastern Australia.

As the "worst storm in decades" struck the country with force, South Australia was plunged into darkness and triple-0 down in isolated parts of the state.

Damage to infrastructure near Port Augusta at 3.48pm yesterday forced the whole electricity network to shut down, according to SA Premier Jay Weatherill.

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Winds over 80km/h brought down a power line on to a car in Port Augusta, SA. Photo / Lauren Rose, Southern Cross, Twitter
Winds over 80km/h brought down a power line on to a car in Port Augusta, SA. Photo / Lauren Rose, Southern Cross, Twitter

He said there did not appear to be any damage to the interconnector with Victoria and that the Australian Energy Market Operator was working to get the power restored.

The Premier said several "weather events" produced wind gusts and thunderstorms so powerful they smashed 22 electricity transmission stations around Port Augusta, which led to the statewide blackout.

SA Power Networks website said about 200,000 properties were without power, with the blackout not expected to be completely over until later today.

Streets flooded in Whyalla, South Australia. Photo / Facebook
Streets flooded in Whyalla, South Australia. Photo / Facebook

Adelaide Hills and northern suburbs were among the worst areas affected.

By 7pm (local time) power had started to be restored to some suburbs, mostly in the metropolitan area's eastern districts.

Hail, winds and wild weather made travel impossible with traffic lights out of action and trams and trains cancelled.

The BoM has warned that gale-force winds of up to 120km/h and plenty more rain is expected across the state today.

Meanwhile, as strong winds from the storm entered Victoria, trees were blown down and there were reports of some flooding in Mildura at about 10pm last night.

Heavy rain is predicted in Victoria for the next two days and emergency services will closely monitor North East and North West Victoria still swamped by recent floods.

Victoria's State Control Centre duty officer Brad Dalgleish said: "We are seeing winds around 70km/h around the Grampians."

Melbourne was expected to get winds about half that speed, but gusts of up to 120km/h are expected to hit the Alpine regions today.

"We are not expecting that it's going to be as extreme as what's happened in South Australia," he said. But he urged residents to be prepared and be vigilant.

The storm will also move into NSW and Tasmania today, while parts of Queensland will also cop a drenching.

Travellers were stranded at Adealide Airport after power cut grounded planes. Photo / Tricia Watkinson, News Corp Australia
Travellers were stranded at Adealide Airport after power cut grounded planes. Photo / Tricia Watkinson, News Corp Australia

Superstorm fury

South Australia was hit first by the storm with roofs blown off homes, and power lines and trees came down across the state.

The state capital's roads were totally gridlocked as police patrols were dispatched to guide traffic at intersections and residents were warned to avoid travel wherever possible.

A few buses were made available for some commuters. Hospitals and some other buildings were operating as normal on back-up power.

The blackout came as torrential rain and winds of 87km/h lashed the state, hitting Adelaide at 12pm yesterday.

Facebook user Julie Minge shared extraordinary footage of golfball-sized lumps of ice battering her neighbourhood in Cleve, SA.

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The BoM had warned super-cell thunderstorms across the central and mid-north districts could produce destructive 140km/h gusts, heavy rainfall, flash flooding and more massive hailstones.

Blackout chaos

SA Ambulance asked South Australians to only call triple-0 in a genuine life threatening emergency and SA Power advised people to conserve their mobile device batteries and prepare for extended outages.

The State Emergency Service earlier advised people to keep their phones charged up in case of power cuts.

Adelaide Airport said flights had been disrupted by the storm and told passengers to check with their airline.

The BoM issued a severe thunderstorm warning for an area stretching from Victor Harbor, south of Adelaide, to Marree.

Major centres to feel the impact of the storms included Whyalla, Port Augusta, Hawker, Port Pirie, Clare, Roxby Downs and Leigh Creek.

The extreme weather dumped 90mm of rain in some areas, including the Adelaide Hills, where a flood warning was in place.

Lightning strikes a tree outside Gary Altman's home in Myrtle Bank, Adelaide. Photo / Tait Schmaal, News Corp Australia
Lightning strikes a tree outside Gary Altman's home in Myrtle Bank, Adelaide. Photo / Tait Schmaal, News Corp Australia

Similar falls were possible in the mid-north with the cyclonic conditions expected to whip up large swells along the state's coastal waters, producing 10-metre waves.

By late afternoon yesterday the State Emergency Service had responded to more than 330 calls for help, most because of fallen trees or rising water. It earlier distributed more than 43,000 sandbags to local residents concerned about possible flooding after severe weather just two weeks ago flooded 80 homes across Adelaide and the Mt Lofty Ranges.

SA fire services warned the public to ensure all heating, cooking and other appliances in use when power went out are switched off.

The bureau said the wild weather was the result of a front and intense low-pressure system.

It said records suggest such a severe system was last reported across SA more than 50 years ago.

Thousands of homes were sandbagged in preparation for super-cell storms, heavy rain and possible flash flooding. Photo / Bianca De Marchi, News Corp Australia
Thousands of homes were sandbagged in preparation for super-cell storms, heavy rain and possible flash flooding. Photo / Bianca De Marchi, News Corp Australia

The BoM had gale-force wind warnings in place for the coastal waters extending from Perth all the way across to Adelaide.

The low is expected to hang around for most of the week, bringing more wild weather across the country.

John Nairn told AAP the weather had the potential to cause widespread destruction. "This depth of low, this close to the coast, is very damaging," he said. "It's a very significant event for South Australia. It's very rare."

Adelaide can expect cooler temperatures as the cold front hits with a low of just 7C on Saturday before further rain hits on Sunday with a top of between 16-18C.