Australia could experience its hottest day on record next week as a hot air mass building in Western Australia makes its way east.

Key points: Perth's blistering heat is expected to end with a cool change sweeping in on Monday

Perth's blistering heat is expected to end with a cool change sweeping in on Monday But the hot air mass fuelling the heatwave will then head across the country

But the hot air mass fuelling the heatwave will then head across the country Australia's current record high temperature of 50.7C at Oodnadatta in SA could fall

Perth is enduring an unprecedented heatwave for December, with the city expected to hover close to 40 degrees Celsius for four consecutive days until Sunday.

But the Bureau of Meteorology (BOM) has warned that as a cool change sweeps in on Monday, the blistering heat will travel interstate.

"We're expecting some incredibly warm conditions as we head into next week, potentially record-breaking for a number of areas across southern Australia over the next seven days or so," BOM meteorologist Diana Eadie said.

"It is not out of the realms of possibility that we could break our highest ever recorded temperature of 50.7C at Oodnadatta, which is in South Australia."

Perth has several more days of near 40C temperatures to come. ( ABC News: Andrew O'Connor )

That record was set on January 2, 1960.

Ms Eadie said there was also a chance Australia could record its hottest day as a whole towards the end of the week.

"So when you combine all of the maximum temperatures recorded on any given day, the hottest on record was on the January 7 back in 2013, when we saw an average maximum of 40.3C," she said.

"At this stage with these sorts of temperatures that we're forecasting … it looks like we could break that record over a number of consecutive days towards the end of next week.

"We will potentially see the hottest day on record across all of Australia."

The heat goes east

The heatwave conditions saw Australia listed among the hottest countries in the world on Thursday.

Australia was listed as the hottest place in the world on Thursday. ( Supplied: Windy.com )

Adelaide, Canberra and western Sydney are expecting temperatures near the 40C mark next week, but the hottest parts of the country will be further inland.

"[The heat] will creep into South Australia initially, we will start to see those temperatures rise over South Australia on Monday and Tuesday," Ms Eadie said.

"But as we go through the remainder of the week, that will extend a little bit further east and become concentrated over parts of Victoria and New South Wales as well.

"Predominantly the areas that look to be affected are north-western and central parts of Victoria, and then mostly southern and western parts of New South Wales will feel exceptional heat.

"But really all of those states and even extending into southern parts of the Northern Territory and parts of Queensland won't be immune."

Hot weather records set to fall in Perth

The first day of Perth's heatwave yesterday just missed out on the 40C forecast, peaking at 39C, but the city has another three days of temperatures close to 40C to go.

Blistering heat is a hallmark of summers in the west but this season has escalated much earlier than usual.

The hottest parts of the country next week are expected to be inland. ( Pixabay: Gerd Altmann )

Perth recorded its earliest December day above 40C on December 3, peaking at 41.6C in what was its hottest first week of summer on record.

The city has never recorded more than two 40C days in December, but that record will be challenged this week.

Currently the city is tracking about 6C above its mean December maximum of 29.1C.

The Health Department has activated its heatwave hazard plan and is liaising with various agencies, hospitals, businesses, infrastructure providers and sporting clubs to minimise the risks of heat to the public.

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