The blazes have claimed three lives and destroyed about 2.5 million acres of farmland and bush fuelled by extremely dry conditions after three years of drought
Australian officials ordered people in several communities, including a major tourist destination, to evacuate immediately on Wednesday as firefighters struggled to contain more than 150 bushfires raging across the east coast.
While cooler weather overnight brought some relief for firefighters in New South Wales (NSW) state, attention shifted to its northern neighbour, Queensland, where hot, dry and windy conditions brought severe fire danger.
Authorities issued a "leave immediately" warning, the highest level, for several areas including Noosa, a beachside holiday destination 150 km (93 miles) north of Brisbane, the state capital of Queensland.
"Conditions are now very dangerous and firefighters may soon be unable to prevent the fire advancing," Queensland Fire and Emergency Services (QFES) said.
"The fire may pose a threat to all lives directly in its path."
Noosa Mayor Tony Wellington told Reuters many of the residents in the affected north, accessible only by ferry or via the beach, had got out this week.
But he added that winds were picking up, making things particularly tricky.
"There are plenty of crews battling the fire, including two helicopters," he said.
The blaze in Noosa is one of more than 80 fires across Queensland, leaving firefighters stretched.
QFES said one of its water-bombing helicopters crashed while battling a fire in Pechey, west of Brisbane, though the pilot escaped with minor injuries.
Bushfires are common in Australia's hot, dry summers, but the ferocity and early arrival of the fires in the southern spring this year has caught many by surprise.
The blazes have claimed three lives and destroyed about 2.5 million acres (1 million hectares) of farmland and bush, fuelled by extremely dry conditions after three years of drought, which experts say has been exacerbated by climate change.
'Out Of Water'
The hot and windy conditions are set to spike again next week.
"We will not have all these fires contained before then," NSW Rural Fire Service Commissioner Shane Fitzsimmons told reporters in Sydney. "We will not have all these fires contained and locked up for many, many weeks."
"Unfortunately, what we need is rain ... and there is certainly nothing in the forecast for the foreseeable future that's going to make any discernible difference to the conditions."
Some 300 homes have been destroyed in NSW in recent days, Fitzsimmons said, as flames stretched from the state's north coast to within meters of homes in Greater Sydney.
No deaths were reported on Tuesday as warning systems and evacuation plans appeared to save lives in the face of what officials said was the greatest threat in at least a decade.
"It was just chewing up everything," Karen Weston told Australian Broadcasting Corp from an evacuation center of a fire near Taree on the mid-north coast. "I've survived two other bushfires before this but never anything like this."
Academy award-winning actor Russell Crowe tweeted photos and video footage on Wednesday of firefighters using helicopters to waterbomb his property near Nana Glen, a rural community some 580 km (360 miles) north of Sydney.
Crowe said the property had "lost a couple of buildings", some fires were still burning and "we are out of water".
The fires have sparked increasingly acrimonious debate over climate and fire-prevention policies, with the ruling conservative Liberal Party and the minor opposition Australian Greens exchanging barbs.
Former deputy prime minister Barnaby Joyce was among those who have suggested that climate activists were at least partly responsible for the fires by lobbying to reduce so-called back burns, fires deliberately lit to clear dry undergrowth.
Deputy Prime Minister Michael McCormack, meanwhile, said linking the fires to the government's support of the coal industry was "the ravings of some pure, enlightened and woke capital city greenies".
Prime Minister Scott Morrison, who has declined to comment on climate change during the crisis, has called for moderation in the debate.