Emergency services are preparing for extreme bushfire conditions over the Christmas break with total bans declared in multiple states.
Hot, dry conditions will hit South Australia on Christmas Day with temperatures in the high-30s expected, prompting a total fire ban for the Mount Lofty Ranges and far west coast.
"We are in one of the driest periods on record in South Australia's history," Premier Peter Malinauskas said on Tuesday.
"That means all we need is heat and wind to combine to create conditions for total fire bans and for high-risk fire weather."
Firefighters were injured on Tuesday in what authorities are treating as a suspicious blaze.
"We've had four firefighters who have been injured as a result of a fire that didn't need to occur and that's the kind of thing that just makes us sick to the stomach," Mr Malinauskas said.
Victorian emergency services are expecting the worst conditions on Boxing Day since the deadly Black Summer of 2019-2020, with Country Fire Authority Chief Officer Jason Heffernan warning blazes would be hard to contain.
The authority has declared a total fire ban for Thursday, a day earlier than when such decisions are usually made.
“There are two major concerns on Thursday - the fires already burning and any new fires that start as a result of the extreme fire risk,” Mr Heffernan said.
People are being told to rethink travel plans on Boxing Day.
"Thursday is some of the most significant fire danger we've seen in Victoria since Black Summer," State Control Centre's Luke Hegarty said.
A 45,000-hectare inferno in the Grampians National Park is expected to spread quickly on Boxing Day, with temperatures forecast of more than 40C and wind gusts potentially sparking spot fires as far as 15km from the fire front.
"It's going to be a very hot day with strong and gusty northerly winds developing and bringing extreme fire dangers to much of the state," weather bureau senior meteorologist Sarah Scully told AAP.
A gusty southwesterly change later on Boxing Day is expected to deliver cooler conditions and even some light showers but could also shift fire fronts and make life harder for firefighters, Ms Scully said.
Temperatures are likely to ease on Friday and Saturday.
About 100 interstate firefighters are coming to help battle the blazes.
Grampians Tourism chief executive Mark Sleeman said the blaze was costing the local economy $1.9 million per day.
"We're going to need some immediate intervention and financial support from both federal and state government to reignite our local visitor economy," he told AAP.
Mr Sleeman almost lost his home in February's Pomonal bushfires and will spend Christmas Day preparing to defend it again while his family stays elsewhere.
"I'll be here until it's not safe to stay and then evacuating," he said.
Another bushfire at Bullengarook in Melbourne's northwest has been contained, while a blaze at the Gurdies in western Gippsland continues to burn.
In NSW, several small bush and grass fires remain live but are under control, though a significant part of the state faces high fire danger on Boxing Day.
In Western Australia, a "too late to leave" alert for residents near the wheatbelt town of Northam in Western Australia was still current late on Tuesday.
