A heatwave stemming from Western Australia is set to strike Adelaide and Melbourne this Saturday, with temperatures predicted to soar to 42 degrees Celsius in Adelaide and 40 degrees in Melbourne.

In Victoria, officials are cautioning that northern regions might experience temperatures exceeding 40 degrees for several days, potentially lasting up to a week.

“A heat dome is anticipated to settle over Victoria, not only affecting this weekend but extending well into the coming week,” stated Kevin Parkyn from the Bureau of Meteorology.

The city of Mildura is expected to reach a scorching 43 degrees on Saturday, prompting an extreme fire danger warning for the Wimmera and South West Districts.

A south-westerly wind change is forecast to bring some relief to the south-west areas of the state, including Melbourne, on Saturday evening. However, the intense heat is likely to persist in the northern regions.

The mercury will be somewhat cooler on the south-west coast on Sunday and Monday, before potentially record-breaking heat returns to the state on Tuesday.

Melbourne is tipped to reach 41 degrees on Tuesday as the trough travels further east, with a top of 43 possible in the suburbs.

The heat will be even more intense up north, with 47 degrees forecast for Mildura, 45 degrees in Bendigo and potentially 48 degrees in Ouyen.

”Many centres are probably going to break their all-time maximum records,” Parkyn said.

Another cool change should begin to bring relief to south-west Victoria by Tuesday afternoon.

Authorities are urging Victorians to be aware of their environment over the long-weekend and to limit the use of campfires.

“We do want people out there in Victoria spending money in regional Victoria, enjoying themselves, but we’ve got a lot of really severe and dangerous weather ahead of us and we just ask that people take care and act responsibly,” Fire Forest Management Victoria Chief Fire Officer Chris Hardman said.

“If you are camping, with the temperatures we’re seeing coming our way, do you really need a campfire at all?”

South Australians are also set to swelter through the heatwave across the week.

The mercury is expected to peak at 42 degrees in Adelaide on Saturday, before dipping slightly to 36 on Sunday and again rising to 43 degrees on Monday.

‘Risk of fire will return’

Fire authorities are warning the heatwave is expected to agitate bushfires still raging across Victoria.

The Wimmera and South West districts will be under an extreme fire danger rating on Saturday, while most other parts of the state will have a high rating.

Hot, dry conditions will persist overnight on Sautrday and could exacerbate fire danger, the Bureau of Meteorology warned.

Blazes in Walwa, Wonnangatta and Mallacoota remain uncontrolled and four others are also still burning.

More than 1500 structures have now been declared damaged or destroyed by fire and a state of disaster remains in place across Victoria.

The largest and most destructive blaze at Longwood was marked as contained at 5pm last night, meaning the fire continues to burn, but its spread has stopped.

The Longwood fire has burned through 144,000 hectares and destroyed 320 homes, with dozens more damaged and nearly 900 outbuildings impacted.

While wind speeds over the week aren’t expected to be as high as the strong gusts on January 9, authorities are asking Victorians to remain vigilant.

“The risk of fire will return,” CFA chief officer Jason Heffernan warned.

“We will be declaring total fire bans throughout the course of this fire event.”

Parkyn warned a dry outlook could make it even more difficult to quash the fires, and any new ones that start.

“We’re not expecting any significant rainfall to affect Victoria over the next two weeks,” he said.

Almost two dozen firefighters have been called in from New Zealand to help bolster efforts.

They will be joined by 74 Canadian firefighters expected to arrive in Victoria early next week.