The warning level for a mammoth bushfire in Australia creeping across Victoria's west has been downgraded as firefighters brace for sweltering conditions on Boxing Day.
The blaze in the Grampians National Park has razed 34,000ha and remains out of control despite more than 300 firefighters battling to bring it to heel and secure containment lines before Thursday.
Emergency warnings have shifted to "watch and act - not safe to return" for tourist hotspot Halls Gap and surrounding areas.
Country Fire Authority deputy chief officer Garry Cook said ground and air crews were working to reduce the spread of the Yarram-Gap Road fire ahead of elevated weather conditions on December 26.
"As we look toward Boxing Day, firefighters are currently conducting back-burning operations to protect nearby towns and establish fire breaks.
"Boxing Day is a big travel day right across the state, so we urge those travelling to download the VicEmergeny App before you go."
Melbourne is expected to roast to 39°C on the public holiday with similar conditions slated for the Grampians, 270km west of the city.
Authorities say it could take weeks to fully contain the fire ignited by a lightning strike earlier in the week and an emergency evacuation warning remains in place for several communities.
The blaze tripled in size between Friday and Saturday due to high temperatures and strong winds.
Similar conditions on Saturday night resulted in the inferno moving towards Halls Gap and Lake Bellfield.
Incident controller Aaron Kennedy said the blaze was burning in very steep, difficult and dry terrain.
"Our ability to fight this fire directly is quite challenging," he said.
Mr Kennedy agreed the fire risk was expected to spike on Thursday and be worsened by windy conditions forecast for the area.
"This will mean that we'll see again, potentially significant fire behaviour, and then increased growth of the fire across the landscape," he said.
"Our crews are working really hard to try and contain this fire prior to the Boxing Day weather event."
Mr Kennedy said two years of dry conditions in western Victoria, particularly in the Grampians National Park, meant fires spread quickly.
The threat to the nearby communities of Lake Fyans, Pomonal, Mafeking and Watgania eased late on Saturday when emergency warnings were downgraded to watch and act, but not safe to return.
Relief centres are open in Ararat and Stawell. The Grampians National Park is closed to visitors.
A blaze at Bullengarook, northwest of Melbourne, was also downgraded to a watch and act.
A bushfire in The Gurdies in South Gippsland was also downgraded to an advice warning.
Fire crews in New South Wales and Western Australia have also battled multiple bushfires in the first weeks of summer.
Temperatures in the high 30s and low 40s are expected to hit WA, including the wooded southwest of the state, over the weekend before pushing eastward.
Elevated fire dangers are forecast for the south and midwest of WA with dry thunderstorms possible for western parts.
Heatwave conditions are forecast for the state's midwest and the Kimberley and Pilbara regions.
Moderate and extreme fire weather conditions are forecast for inland parts of NSW in coming days, including the greater Sydney area.
