Hot, dry, windy conditions have been building across the nation since Christmas Eve, fuelling bushfires including a massive blaze in Victoria's Grampians National Park.
Birdsville, in southwest Queensland, recorded 47.2C on Boxing Day, the nation's highest temperature, while Moomba in South Australia hit 45.5C.
The extreme conditions have complicated firefighting efforts in the Grampians, where wind gusts reached 95 km/h.
Half of the iconic Grampians region in Victoria is on fire, about 74,000 hectares.
Sweltering temperatures and high winds have fuelled bushfires in the Grampians. (James Ross/AAP PHOTOS)
A dramatic cool change brought some relief overnight, with temperatures dropping 10C in two hours at the fireground.
However, the weather bureau said the change did not bring any relief for firefighters in the form of rain.
"No rainfall was observed across the Grampians northern fire sites with this system," said the Bureau of Meteorology's Jonathan How.
The potentially dangerous weather pattern has now shifted northeast, with Sydney facing extreme fire danger ratings on Friday.
⚠️Fire Weather Warning— Bureau of Meteorology, New South Wales (@BOM_NSW) for the Greater Hunter, Greater Sydney Region and North Western fire weather districtsExtreme Fire Danger is forecast with fresh and gusty northwesterly winds combined with hot and dry conditions Details: https://t.co/bK2ikP72VI pic.twitter.com/xmcVIll85kDecember 26, 2024
Western Sydney is bracing for temperatures in the low 40s, while coastal areas expect high 30s.
"With that heat and also very dry winds coming through from inland areas, we are expecting extreme fire dangers for Sydney and Hunter as well as the northwestern slopes of New South Wales," Mr How said.
A total fire ban is in place for those areas.
Queensland isn't being spared, with Brisbane set to peak at 37C on Saturday and the city's western suburbs potentially reaching 40C.
The bureau warns of "low to locally severe intensity heatwave conditions" stretching along Queensland's east coast.
A cool change if offering relief to southern states, with temperatures dropping 10-15 degrees in Victoria and SA later in the weekend.
Melbourne and Adelaide are expecting much milder conditions of about 22C on Friday.
The Bureau of Meteorology is urging residents to stay updated on local fire authority advice and to check current conditions.
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