Western Australia's north has experienced another sizzling day amid an extreme heatwave, with one location falling 0.2C short of its highest ever recorded temperature.

The Bureau of Meteorology's Neil Bennett said some places in the state had already broken January heat records.

"The reason for the [heatwave] has been a slow moving area of very, very hot air that has not moved out of that Pilbara/Gascoyne area," he said.

"So we have got this pool of very hot, slow moving air over the region and we think the peak of the temperatures will occur on Friday, and then it will slowly slide eastwards."

On Tuesday Carnarvon hit 47.8 degrees Celsius, equal to its hottest ever day.

Beating the heat: Kev Danks outside his spinifex shed at Marble Bar. ( Supplied )

Earlier in the day Mr Bennett said Marble Bar could get close to its hottest ever day on record - 49.2C, recorded on January 11, 1905, and January 3, 1922.

But Marble Bar was just 0.2C shy and hit a maximum of 49C at 3:12pm, while the next hottest, Shay Gap, reached a maximum 48.3C at 12:44pm.

Marble Bar resident Kev Danks said he would be escaping the heat over the next few days in his purpose-built spinifex shed.

"It's like a room, or whatever, a shed, but instead of having tin walls it has got about 4 inches thick of spinifex [grass] between two bits of wire," he said.

"You have water running around a pipe with holes in it, and the water runs down that, and hopefully you get a bit of breeze and you get a bit of coolness.

"Fortunately I have got some solar power in it and I can put a fan on, and it's not bad."

Roebourne resident Robert Bropho keeps his beanie on, despite extreme temperatures predicted. ( ABC News: Alexia Attwood )

Roebourne resident Robert Bropho said while he was staying home, most people would head out bush where it was cool, to fish or swim.

He said it rarely rained in Roebourne.

"Only when a cyclone comes, ... it's like there is a big umbrella here," he said.

Another Roebourne resident, Jenny Bailey, said she felt bad for anyone who had to leave their home today, but the heat was par for the course.

"It's a regular day because we get a lot of hot days over 45, so you stay inside if you can and drink lots of water," she said.

Mr Bennett said Mardie Station, which recorded WA's hottest ever temperature of 50.5C in February 1998, could also nudge its hottest ever January day of 49C.

He said Newman and Pardoo may experience their hottest ever January temperatures, but he said it depended on how the day developed.

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50C day 'too close to call'

Mr Bennett stopped short of forecasting a 50C day, which he said had only been recorded three times in Australia.

"In some respects there is a possibility, in other respects it is something we think is too close to call right now," he said.

"It only needs a very subtle change in wind direction for a period of time and that temperature just gets pulled down ever so slightly."

Mr Bennett said the North West was among some of the hottest places in the world.

"Even though we don't call it a desert... it's baking through the Pilbara in the heat of the summer," he said.

Some relief for Marble Bar residents is expected on Sunday, with a top of 43C predicted.

The record for the hottest ever day in Australia was set by Oodnadatta in South Australia in 1960, when the mercury tipped 50.7C.