Victoria is facing a record-breaking run of heatwave conditions over this Australia Day long weekend and into next week.
Adelaide ticked over 41.5 degrees today, while in other parts of the state, temperatures nudged towards 50 degrees with 48.2 degrees recorded in Tarcoola.
Melbourne followed closely, with the city sweltering in 40 degree heat, halting play at the Australian Open.
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The heat also sparked emergency level bushfires in Victoria's south-west, with multiple evacuation orders in place as firefighters attempt to contain the blaze.
A total fire ban is in place for the entire state of Victoria, while South Australians face catastrophic fire danger on the Yorke and Eyre Peninsulas.
In South Australia, south-westerly winds will knock temperatures back a few degrees tomorrow – down to 37 degrees in the city – but Adelaide could hit 45 degrees on Monday, making it the hottest Australia Day on record.
Some relief may be on the way for Victoria but it won't last long, with Tuesday looking even hotter.
"We've got a trough that's pushing into south western parts of the state," Bureau of Meteorology senior meteorologist Sarah Scully said.
"The gusty north-westerly winds can keep the temperatures really elevated ahead of that cooler south-westerly change."
Bureau of Meteorology senior meteorologist Christie Johnson said northern parts of Victoria could see temperatures into the 40s for potentially five or six days in a row.
Johnson said Tuesday could be a day of concern with near-record temperatures of about 48 degrees.
"It could definitely be one of the hottest days that we've ever seen over Victoria," she said.
Water police will be out in force with hundreds expected to pack beaches across the coast over the long weekend.
"Take care on our beaches, take care on our waterways and take care on our roads," Victoria Police acting superintendent Brett Coloe said.
"It's going to be a very, very busy period."
Residents have been warned to take care as the blistering sun can be deadly.
"Hot weather not only creates its own emergencies with people becoming dehydrated and leading to heat stress and stroke, but it can exacerbate normal medical problems as well, which increases our workload," Ambulance Victoria's Andrew Burns said.
'Catastrophic fire dangers'
Scully told Today there's the potential for temperature records to be broken, amid increased fire dangers.
"What this means is if any fires are ignited, they will most likely be impossible to control," Scully said this morning.
"Now, broadly speaking, when we do have catastrophic fire dangers in place, it's recommended that people leave early.
"However, it's important for any of the residents within these areas to listen to the advice from local emergency services."
Tennis impacted
Australian Open matches in Melbourne were halted after the Heat Stress Index reached five.
Matches at the tournament had started half an hour early, so players could avoid the sweltering conditions.
"We're assuming that the heat is not going to go away and we need to keep players safe," Chief Medical Officer for Tennis Australia, Caroline Broderick, told Today.
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"When the heat stress scale hits three, we have additional cooling measures on court.
"When it hits four, we have these rest breaks between the second and third set in women's tennis and the men's tennis.
"Heat stress scale hits five, we cancel or postpone all play on outside courts and close the roofs on our stadium courts."
South Australia on track for record-breaking heat
South Australia has sweltered through a day of extreme heat with some parts of the state, reaching close to 50 degrees.
The extreme conditions have seen events cancelled across the state, with the latest casualty the Australia Day fireworks at Elder Park.
Aus Lights on the river's been scrapped for the first time in its history but the Mourning ceremony should still go ahead.
"Make no mistake, the state is set to bake for much of the next week," the Bureau of Meteorology's John Fisher said.
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Emergency Services Minister Rhiannon Pearce said additional aircraft, including a large aerial tanker, would be deployed if required across the state.
Those planning long weekend road trips have been asked to think twice.
"Don't go into the highest risk fire areas, and if you are and you have accommodation booked, please be sensible about it," Loughlin said.
High electricity demand could also cause significant strain, making power outages a possibility.
"Common sense – we can do this, we can get through this hot weather if we work together and we make sensible decisions," Loughlin said.
Tropical Cyclone crosses WA cost
On the west coast of Australia, residents along the west Kimberley coast are feeling the effects of Tropical Cyclone Luana.
The Category 2 storm crossed the WA coast north of Broome – between Beagle Bay and Cape Leveque – this afternoon [AWST] bringing destructive winds of up to 130km/h and heavy rainfall.
A warning zone extends from Broome to Kuri Bay, including Derby and adjacent inland areas, with a severe weather warning in place for heavy rainfall and flash flooding about the central and northern Kimberley.
The bureau warns of six-hour totals of up to 120 millimetres, with heavy falls bringing possible 24-hour totals of up to 200mm along the coastal fringes.
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