Weather chaos: Worst storm' ever strikes - and now a heatwave warning

Australia has been hit by wild weather, with a devastating storm lashing South Australia just as large parts of the country are being warned to brace for an intense heatwave this week.

A freak storm smashed the town of Port Pirie, on the east coast of the Spencer Gulf in South Australia, on Saturday.

Thousands of residents faced power outages as the severe thunderstorm brought large hail and damaging winds, which ripped out powerlines, brought down trees, and destroyed houses.

Footage showed trampolines being flung down the street as wind gusts reached 119 km per hour just after 8 pm.

There was so much hail that residents reported it appeared the town had a dumping of snow.

Emergency services labelled the weather event as the 'most significant storm' to hit the region on record, with the SES receiving more than 350 call-outs for help.

SES acting chief officer Kirsty Phelps said the storm caught emergency responders by surprise, with residents facing a massive clean-up in the wake of the storm.

'This is the most significant storm event we've had in the Port Pirie region on record,' she said.

A freak storm smashed South Australia's Port Pirie on Saturday, with large hail and damaging winds ripping out powerlines, bringing down trees and destroying houses

South Australia Premier Peter Malinauskas said the severe storm cell stunned residents as it was 'not anticipated by the Bureau of Meteorology'.

He added that at least two homes were destroyed; however, the majority of the damage in town occurred due to fallen trees.

About 4,900 households were left without power at the storm's peak - equivalent to the damage expected during a prolonged weather event on a statewide level.

Meanwhile, an intense heatwave is set to hit large parts of the country this week, with temperatures predicted to reach a sweltering 46 to 47C in at least two states.

A burst of late-spring heat is set to develop over the country's interior as Tropical Cyclone Fina, which is bearing down on the Northern Territory's Top End, draws vast amounts of heat from the Timor Sea into the atmosphere.

Weatherzone Meteorologist Ben Domensino explained the upper-level air will move south from Monday and spread over the country.

'While [the air] has lost a lot of the moisture it began with, it has retained its potential temperature,' he said.

'This means the air will warm up as it descends towards the ground over central Australia this weekend and early next week, a process called adiabatic warming.'

There was so much hail that residents reported it appeared the town had a dumping of snow (pictured)

The freak storm caused the roof of several homes to collapse, leaving residents with a massive clean-up operation

He added temperatures on Monday are forecast to reach a whopping 45 to 46C in South Australia and a scorching 47C in southwest Queensland.

Northwest NSW and the southern part of the Northern Territory will also feel the heat, with the mercury expected to hit the low to mid 40s in the coming days.

Mr Domensino said the hot weather was not unprecedented for central Australia in late spring but could potentially reach within a degree or two of November records.

Weatherzone and the Bureau of Meteorology are expected to issue heatwave warnings for several states and territories over the coming days in response to the rapid onset of intense heat.

BoM meteorologist Dean Narramore warned Aussies to brace for 'severe to severe heatwave conditions' as many parts of Australia will see temperatures between 4 to 10C hotter than average.

These temperatures will impact inland parts of South Australia, Queensland, NSW, Victoria and Tasmania on Monday and Tuesday.

Meanwhile, residents living along NSW and Queensland's east coast will feel the hottest days between Wednesday and Friday.