A fire in the Grampians, Victoria, Australia, has now spread to more than one-third of the national park, with authorities warning those in surrounding areas to remain alert ahead of quickly-changing conditions on Thursday afternoon.
Emergency Warnings are in place for dozens of towns in the Grampians.
Authorities say the bushfire has grown to more than 66,000 hectares.
The State Control Centre's Luke Heagerty said at 4:45pm there had been significant fire development in the Grampians on Thursday afternoon as the first wind change swept through.
"(It's) really starting to affect parts of the fireground," he said.
"We've seen expansion of the fire to the south-east this morning and early this afternoon with the north-easterly winds.
"Now we've seen parts of the fireground become affected by the wind change moving through."
The Bureau of Meteorology's senior meteorologist Michael Efron said strong winds have hit parts of the state, including winds of about 95 kilometres per hour in Longerenong, near Horsham, just after 2:30pm.
"But around 6pm, we're going to see a westerly wind change move through that area, and so winds associated with that change may reach 80 to 90 kilometres an hour in that Grampians area, or even 100kph about the highest peaks," he said.
"People may think getting towards sunset, the danger's easing, the concern is around that 6pm or 7pm period, the winds will actually strengthen in that area."
A cool change is expected to hit Melbourne about 9pm, with gustily south-westerly winds moving through," Mr Efron said.
"We'll see the temperature drop around 10 degrees in about half an hour."
He warned anyone in bayside suburbs to be careful of the winds as they came through.
No residential property losses so far, say authorities
Victorian authorities have had no reports of homes lost in the Grampians National Park bushfire so far, but say they "wouldn't be surprised" if that changes at some stage.
Speaking at a press conference at 1pm on Boxing Day, Victorian Emergency Management Commissioner Rick Nugent said there had been stock losses, as well as damage to fencing, and outbuildings such as sheds.
"We have no reports as yet of residential homes (being lost), but there are many residential homes in the bush areas on the edges of the Grampians, so I wouldn't be surprised at some point if we have residential losses," he said.
"But firefighters I can say are doing everything possible to protect life and protect property in what they are doing."
Mr Nugent said authorities were concerned about four existing fires in particular - the Grampians fire, The Gurdies fire near Lang Lang, the Bullengarook fire near Gisborne, and the Creswick fire near Ballarat.
A total fire ban is in place for the entire state, as well as an "extreme" fire danger rating, except in East Gippsland, where the risk has been deemed as "high".
Authorities have urged people to avoid all non-essential travel through those areas deemed at "extreme" risk.
There are relief centres at Stawell, Ararat and Hamilton for those affected by the out-of-control Grampians fire.
Mr Nugent said he expected the Grampians National Park fire would burn for weeks, and would be "extremely difficult" to put out.
Family leaves property on Christmas Day
Bec Star lives at Black Range, which is east of the Grampians National Park fire.
She told the ABC she left her family property on Christmas Day and evacuated to Stawell.
"I got Mum packed up yesterday too as we live on the same property … along with her dog and cat," she said.
Ms Star said it was "devastating" to see nearby Mount William "go up in smoke".
"I'm third generation on our land, [our property] was my grandfather's favourite place in the world," she said.
"It's just so hard to feel so helpless when the mountains I love so much are burning."
Moyston resident Daryl Lord, who bought a property with his wife six years ago, said he was feeling "apprehensive" today.
"The proposed weather conditions are a concern because all of the fire is to our west and if the predicted winds from the west come, it blows it all on to us at pretty high velocity."
He said warnings that Boxing Day conditions could be as bad as Black Summer seemed realistic.
"The problem is that it's unpredictable where and when, and that's the hard part," Mr Lord said.
"Literally we could cop it from any direction."
Authorities 'prepared for fires across the state'
High temperatures and gusty winds are expected to elevate the bushfire risk in most parts of the state on Thursday, with some regions predicted to experience conditions similar to those of the 2019/20 Black Summer bushfires.
Mr Nugent said the wind conditions would make it hard to contain the other three fires of concern at The Gurdies, Bullengarook and Creswick.
He said any new fires that begin today would also prove difficult to fight due to the expected wind change later in the day.
"We've prepared for fires today across the state," Mr Nugent said.
Temperatures on Thursday were expected to soar to between the high 30s and low 40s in the state's north, with gusty northerly winds over western and central districts anticipated, ahead of a strong south-westerly change.
But the Bureau of Meteorology said temperatures had been a touch lower than forecast in some places because of cloud cover.
The highest temperatures have been recorded in the north-west, including Mildura with 41.5 degrees Celsius and Swan Hill with 40.3C.
Kyabram, in north central Victoria, has reached 40.6C, while Melbourne hit 36.7C just after 4pm.
In Stawell, the closest weather station to the Grampians, the temperature reached 36.2C about 1pm but has since dipped.
Assistance available for some areas
Acting Deputy Premier Ben Carroll thanked Victorians for heeding today's warnings, and following advice from authorities, but said the threat was not over.
"Dangerous fire conditions are forming today and will go right through to Saturday," he said.
"We know this is a challenging time for all communities, and all communities will be supported through this period."
Government disaster assistance is now available for those affected by the fires in Southern Grampians, Northern Grampians, Ararat and Macedon Ranges council areas.
Residents can find more information at disasterassist.gov.au.
Authorities investigating fire near Bendigo
Police are investigating a suspicious bushfire near Bendigo on Thursday morning.
Crews were called to reports of two separate fires around Munroe Road in Mandurang at 7:20am.
The blaze burnt around 1 hectare before it was brought under control.
Police are asking for anyone with further information or dash cam footage to get in touch with Crime Stoppers.
Grampians fire grows on Christmas Day
Earlier, incident controller Mark Gunning said the Grampians fire, which has burned all week, had spread further on Christmas.
"The fire overnight has grown, it's created its own fire conditions in the last few hours," he said.
"It's well over 50,000 hectares now, so a fire of that size just poses so many dangers in so many parts of the fire at once."
Multiple communities in the area are at risk. Halls Gap was evacuated at the weekend, while residents of Moyston and Pomonal were ordered to leave immediately about 3pm on Christmas Day.
Mr Gunning warned communities to the southern end of the fire such as Dunkeld to stay alert and prepare for the worst.
"If you are on the south or east side of this fire, today is the day you need to be on the top of your game," he said.
"On days like today, if you live in a high-risk bushfire area, the only 100 per cent way to guarantee your safety is not to be there."
- This article was first published by the ABC