Parts of south-east Australia are bracing for another wave of extreme heat over the long weekend and beyond, with possible record-breaking temperatures and extreme to catastrophic fire danger.

The Bureau of Meteorology is predicting the mercury will hit 40 degrees in Melbourne on Saturday – potentially triggering the Australian Open’s extreme heat policy, which allows extra breaks for players and even the suspension of matches.

South Australia is also set to swelter on Saturday, with 42 degrees expected in Adelaide on the second-to-last day of the Tour Down Under international cycling event.

Race director Stuart O’Grady told Cycling News that race organisers would be keeping a close eye on the risk of fires in the Adelaide Hills, but added: “I haven’t heard of a race yet that’s been cancelled or postponed due to the heat.”

Most of South Australia is expecting high to extreme fire danger on Saturday, while the Yorke Peninsula will face potentially catastrophic fire danger, according to the BOM.

The extreme fire danger extends into parts of western Victoria.

“The combination of heat and wind, and also the very dry fuels from recent heat, creates a very high risk of bushfires, also making them hard to fight,” warned meteorologist Christie Johnson.

A heatwave in Victoria could affect the Australian Open. Image: Weatherzone

The heatwave began in Western Australia, where extreme temperatures were recorded in a number of locations during the week – including Shark Bay airport (gateway to the tourist spot of Monkey Mia), which reached 49.2 degrees.

While most of the country’s south coast will get a reprieve from the extreme heat on Sunday, it won’t last long. After redeveloping over southern parts of Western Australia, it is expected to build again at the start of the week over SA, NSW and north-western parts of Victoria.

In South Australia, it may even be too hot to spend the Australia Day public holiday at the beach, with 43 degrees expected in the capital on Monday and the mid to high-40s in other parts of the state.

The forecast has forced the cancellation of an Australia Day parade, with other events pushed back until early evening, when a cooler change is expected.

Ooodnadatta, in SA’s far north, is sweltering with temperatures from 43 to 48 right across the next seven days.

The BOM reports that Tuesday could be the peak for north-western Victoria, where 47 degrees – a January record – is currently forecast for Mildura. Melbourne is expecting 41 degrees.

NSW may have its hottest day on Wednesday, again with potentially record-breaking temperatures.

“And the heat even lingers into Thursday,” Johnson said. “In fact, it might take until next weekend for us to see  that heat flushed all the way out.”

The bureau warns that heatwaves can be especially dangerous for vulnerable people, including the very young and very old, pregnant women, and those who are ill.

“Extreme heatwave conditions are very dangerous for everybody if you don’t take precautions to stay cool,” said Johnson.