Emergency services used milder conditions in the days before Boxing Day to make final preparations such as back-burning and creating fire breaks. Victorians have been warned to stay abreast of emergency warnings and to avoid any unnecessary travel on Thursday.

In Melbourne, a high of 40 degrees is forecast in some suburbs with a cool change expected to sweep through in the evening. Near the Grampians fire, Halls Gap has a predicted high of 32 degrees, and Stawell and Ararat a peak of 37 degrees.

Loading

A severe weather warning for damaging winds was announced for much of western Victoria on Wednesday. Bureau of Meteorology senior meteorologist Dean Narramore said gusts reaching 100km/h would inflame any existing or new fires.

“With these hot, dry and windy conditions, any fires that do get going are likely to be uncontrollable and uncontainable,” Narramore said.

“Obviously concerned definitely around the Grampians with the fire there at the moment, with these strong gusty winds, then that westerly wind change coming in. Big concern for the fire areas and the communities around the Grampians fire.”

On Tuesday, Halls Gap residents were granted a two-hour window to make mercy dashes into the town so they could retrieve personal belongings and finalise their defences.

State Control Centre spokesman Luke Hegarty has urged Victorians to make sure all fires are out by midnight on Wednesday.

“If you’ve been camping, if you’ve been out in the bush, or if you’ve been working at home ... Check any fires, make sure they’re fully extinguished and help keep Victoria safe,” Hegarty said.

Elevated risks of heat-related health issues are expected, including heat cramps, heat exhaustion and heat stroke, Ambulance Victoria emergency management director Dale Armstrong warned.

Heat stroke is fatal in up to 80 per cent of cases.

“Most at risk are elderly people, young children and those with medical conditions, however, heat and heat-related illnesses can affect anybody,” Armstrong said.

Victorians have been urged to prepare for outages, with energy network company AusNet warning power faults could be triggered to prevent bushfires starting on Thursday.

As a cool change washes over Victoria on Friday, the extreme fire dangers will push into parts of central north-eastern NSW on Friday and Saturday.

South Australia, Western Australia on alert

A high-pressure trough making its way across Australia has also brought fire danger to parts of Western Australia and South Australia on Christmas Day.

Adelaide was set to record its hottest Christmas since 2016, with the mercury expected to reach 37C, and top 40C in other parts of the state.

Total fire bans have been declared in the Mount Lofty Ranges and the west-coast region of South Australia, and also in Western Australia from Perenjori down to Quairading, east of Perth.

South Australia is in one of the driest periods on record, Country Fire Service chief officer Brett Loughlin said on Wednesday, warning fires could spread rapidly.

“All we need is heat and wind to combine to create conditions for total fire bans and high-risk fire weather,” Mr Loughlin said.

“This is not something that we do lightly.”

South Australian premier Peter Malinauskas has urged people to enjoy the festive season but to act sensibly and cautiously if they are in bushfire zones.

Start the day with a summary of the day’s most important and interesting stories, analysis and insights. Sign up for our Morning Edition newsletter.

With AAP