Parts of Australia will face catastrophic fire conditions on Friday, when heatwaves are expected to hit most of the country.

Severe to extreme heatwaves have been declared in every state and territory in Australia, except for Queensland, with high temperatures forecast for days.

The state of Victoria has declared a total fire ban for Friday, as the fire danger rating will be set at "catastrophic" - the highest level. Some 450 schools and childcare centres will be closed.

One meteorologist told the BBC that the combination of heatwaves and an elevated fire danger in parts of the country could create the most "significant" conditions since the devastating Black Summer bushfires.

On Thursday, firefighters battled several blazes in Victoria and New South Wales (NSW), with a dozen planes carrying water called in to tackle a large fire near the city of Wodonga, the ABC reported.

Melbourne experienced its hottest day in six years on Wednesday with a high of 40.9C (105.6F), while some coastal towns in Western Australia hit 49C.

In NSW, the heatwave is expected to peak on Saturday with Sydney facing a high of 42C while areas of South Australia and Western Australia will see temperatures over 40C in the coming days.

Friday will be the "real peak of the current burst of heat," Angus Hines from the Bureau of Meteorology told the BBC.

"It will be a very hot day for almost all of South Australia, Victoria, most of New South Wales, parts of Tasmania".

Wednesday was the first significant heatwave for Melbourne and Adelaide, where millions of people live, with fire conditions set to worsen on Friday, he said.

"Firstly, the winds are strengthening across Victoria tomorrow," Hines said, adding that coupled with possible thunderstorms with little rain and dry lightning strikes, the fire danger will hit catastrophic levels for the northern parts of Victoria.

"This looks like the most significant event at a multi-day level for inland south-east Australia since 2019-2020," Hines said.

That period six years ago saw Australia's most severe fire season on record, the so-called Black Summer where dozens of people died and tens of millions of hectares of land was burnt.

In Victoria, authorities on Thursday warned that a catastrophic fire danger rating means potential blazes can be "unpredictable and uncontrollable".

"We need the community to play their role alongside our emergency services to protect lives and property," said Victoria's Emergency Management Commissioner Tim Wiebusch.

"Prepare now and enact your bushfire survival plan. If you are in an area of forecast catastrophic fire danger, leave early to an area with a lower fire risk."

Australia's fire danger ratings scale has four levels, with catastrophic being the highest level, followed by extreme, high and moderate.

A heatwave is declared when the minimum and maximum temperatures are expected to be unusually high for three days of more.