Temperature records have been broken in parts of South Australia, Victoria and NSW, with Victoria recording its highest ever temperature, according to preliminary observations released by the Bureau of Meteorology (BoM) on Tuesday.
The temperature at South Australia's Renmark Airport hit 49.6C just after 2.20pm, surpassing a previous record of 48.6C from December 2019.
Mildura, Victoria, hit 48.6C at 4.40pm, exceeding the 46.9C recorded in January 1990.
The mercury in the towns of Walpeup and Hopetoun soared to 48.9, which exceeds the previous highest daily maximum temperature of 48.8C in Victoria.
In Broken Hill, in outback NSW, temperatures reached 47.8C, a degree higher than the previous record set in 2001.
The BoM said records would be confirmed when official figures became available on Wednesday morning.
Bushfires burn out of control
Statewide fire bans are in place for Victoria and South Australia as multiple blazes burn out of control amid tinderbox conditions.
The bushfire at Carlisle River in the Otways Ranges, in south-west Victoria, is causing serious concern, after breaching containment lines over the weekend.
At least three homes are believed to have been lost in the fire, although it's not clear if they are primary places of residence or holiday homes.
Authorities expected a strong south-southwesterly wind change on Tuesday afternoon, which would create erratic and extreme conditions in the Otways.
Wind gusts of up to 70 km/h were forecast for the region from 5pm.
"That fire will run. It will develop a plume and it will pick up really significant energy," Forest Fire Management Victoria chief fire officer Chris Hardman said.
"The heat conditions are making things incredibly difficult for firefighters in Victoria."
Townships of Barongarook, Gellibrand, Kawarren and Lovat have been added to the evacuation warnings.
Disruptions to Australian Open
The heatwave disrupted the Australian Open tennis for a second time this tournament in the early afternoon, with organisers suspending play on all outside courts at Melbourne Park after determining conditions had reached level five on the Open's heat stress scale.
The roofs of Rod Laver and Margaret Court arenas were closed so the men's singles could continue.
Melbourne reached 42.7C just before 5pm.
"We have seen some all-time records broken around Walpeup, Hopetoun and Mildura," Michael Efron of the Bureau of Meteorology said in an afternoon press conference.
"We are seeing a number of those breaking in weather stations that have been around for at least 50, 60 years. So, certainly a significant heatwave event, not just for Victoria, but for south-eastern Australia."
Extreme heatwave warnings were in place across large parts of NSW, including the Snowy Mountains, south-west slopes and upper western regions.
While Mildura residents were familiar with extreme heat, Mildura mayor Ali Cupper had said the forecast was "unheard of".
"If you're out in the heat, a couple of degrees can be the difference between life and death," she said.
The region is set to swelter through multiple days of 40C-plus heat until conditions moderate from Sunday.
Cupper urged locals to put out water for local wildlife, stay indoors when possible, and monitor for the latest weather updates.
While conditions are most extreme in the regions, the slow-moving heatwave has not spared the cities.
After sweltering through its hottest night on record, with the temperature not dipping below 34.1C, Adelaide got off to a scorching start on Tuesday, crossing 41C by 9.30am.
The temperature in the city reached 44.7C on Monday, topping its previous Australia Day heat record from 2006.
A cool change brought some reprieve to the capital shortly after midday and is set to deliver cooler conditions throughout the afternoon and evening.
Severe heatwave warnings were also in place for parts of the Northern Territory, the ACT and Queensland.
'Extraordinary' pressure on electricity grid
Electricity demand has jumped as people rush to keep homes and businesses cool, though heatwave states have been assured there's enough supply to ward off widespread outages.
Evenings are among the toughest times for energy networks as solar generation starts to wind down just as people return home and switch on their air conditioning units.
South Australian Premier Peter Malinauskas said demand on the network was "extraordinary" but still off the peaks seen in other times.
"So for as long as that trajectory continues, there's no suggestion of any risk at this stage," he told ABC radio.
Victoria's energy minister, Lily D'Ambrosio, said the state had "quite healthy" electricity supplies.
"Despite the fact that today we're looking at new records being broken, the market operator is very confident that we have more than sufficient reserves in place to meet our electricity needs today."
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