Alerts for an out-of-control bushfire burning north of Perth and another in WA's south-west have been downgraded amid easing conditions after a blistering three-day heatwave.

Key points: Perth had a run of three 40C-plus days, the first ever recorded in December

Perth had a run of three 40C-plus days, the first ever recorded in December Firefighters welcomed a cooler change but Perth still reached 38C on Monday

Firefighters welcomed a cooler change but Perth still reached 38C on Monday A fresh emergency warning issued for a bushfire near Collie was downgraded late on Monday

A watch and act alert was in place on Monday night for a fire about 60 kilometres north of Perth, with the warning covering people in the Woodridge, Seatrees and Breakwater estates and Caraban and Wilbinga in the City of Wanneroo and Shire of Gingin.

Authorities said the warning had been downgraded from emergency level as weather conditions were easing and containment lines were continuing to hold the fire.

The fire is contained but not controlled and remains stationary, with winds expected to ease further overnight.

A bushfire advice alert was still in place for Guilderton, Eglinton, Sovereign Hill, Redfield Park, Yanchep, Two Rocks, Gabbedah and Neergabby.

Temporary evacuation centres remained open at Gumblossom Community Centre in Two Rocks and Granville Civic Centre in Gingin.

The Yanchep fire has been burning since Wednesday, but has been downgraded to a watch and act. ( ABC News: James Carmody )

About 13,000 hectares has been burnt since the fire broke out on Wednesday.

It was fuelled by a heatwave that broke December records, with temperatures in Perth topping 40 degrees Celsius for three consecutive days before cooling slightly to 38C on Monday.

A petrol station and one home were seriously damaged the day the fire started, but since then no other homes have been impacted by the flames.

Parts of Breakwater Drive, Yanchep Beach Road and Indian Ocean Drive remain closed, but schools in Yanchep and Two Rocks are expected to reopen on Tuesday morning, along with Yanchep National Park.

Emergency warning for Collie fire downgraded

A second emergency warning was also downgraded to advice late on Monday, for a bushfire near Collie that escalated after strong winds saw it break through containment lines and spread east at rates of up to 1,000 metres an hour.

Authorities said winds had pushed fire away from homes, alleviating the threat to lives and properties from Yourdamung Road in the west, to Trees and Stockyard roads in the north, Quindanning-Darkan Road in the east and Collie-Williams Road in the south.

An exhausted volunteer firefighter took a break yesterday at the Collie bushfire, which has burnt 7,400 hectares. ( ABC News: Anthony Pancia )

Incident controller Brad Barton told ABC Radio Perth there was a lot of work to be done in order to contain the fire, which broke out on Saturday.

"Some pretty amazing fire conditions are being seen. We'll have crews on it overnight and again tomorrow," he said.

"We're hoping that we will get around it eventually but it's being very challenging at the moment."

Australia's biggest firefighting aircraft, the Boeing 737 large air tanker, was sent to WA. ( Supplied: New South Wales Rural Fire Service )

About 130 firefighters are battling the blaze and some resources are being re-deployed from the Yanchep fire to help.

Four fixed-wing water bombers, four helicopters and a Boeing 737 large air tanker borrowed from New South Wales are also taking part in the operation.

The fire has burnt through more than 8,450 hectares of land.

Collie-Williams Road has been closed between Yourdamung Road and Quindanning-Darkan Road, and Opossum Spring Road also remains closed.

Inside the Yanchep fire zone

Members of the media were allowed into the Yanchep fire zone for the first time since flames tore through the area on Wednesday.

State Emergency Services crews inspect cars burnt out by the fire near Yanchep, in Perth's north. ( ABC News: Frances Bell )

The Yanchep petrol station and an adjoining house are so far the only properties that have been impacted by the fire, despite it remaining at emergency warning level for six consecutive days.

The once-thriving small business has been reduced to a pile of twisted metal and ash and several vehicles around the station were also gutted by the flames.

The Yanchep petrol station was severely damaged by a bushfire in Perth's north. ( ABC News: Frances Bell )

Locals referred to the station as an "icon" of old Yanchep and said the owners would be devastated at the damage.

"[The owners are] a real community family, they're always helping everyone out so I hope we can do the same and help them," resident Tara Annandale told the ABC last week.

The Yanchep petrol station was a well-known part of the community in Perth's north. ( ABC News: Frances Bell )

Just metres away, the front garden surrounding the house next door was burnt out, but remarkably the house itself was saved.

Throughout the fire zone, there are examples of just how close the flames came to houses.

In Two Rocks, manicured gardens were untouched by flames that blackened scrubland on the other side of the road.

Locals fled to safety as 'huge glow' loomed

Two Rocks resident Bob Hysen said he was evacuated from his house late on Thursday night.

"I got an almighty knock on the front door and I looked out the front door and there's a huge glow coming up over the hill. I just ran around and grabbed what I could," he said.

Bob Hysen makes wooden fire engines as a hobby and plans to send one to the fireman who saved his property. ( ABC News: Frances Bell )

Mr Hysen said he headed to the Two Rocks marina to escape the flames.

"It was horrendous really. Down at the marina it looked worse because I was looking back and I could see the direction it was heading towards [my] house," he said.

He returned home the following morning to find his front yard and house untouched by the flames.

"When I pulled up here there was a fireman in my backyard and I thought 'oh no, the pergola's gone', or whatever," he said.

"But then he came up and said keep an eye on the palm tree because that caught fire, and my Bali hut is singed and he put that out.

"Then [the fireman] left a note for me [which said] 'sorry about the Bali hut roof, keep an eye on the palm it caught alight up top', with a smiley face."

Mr Hysen, who makes model wooden fire engines as a hobby, said he would sent one of his creations to the fireman as a token of appreciation.

Cooler change offers fire crews an opportunity

Department of Fire and Emergency Services (DFES) Commissioner Darren Klemm told ABC Radio Perth fire crews had made progress containing the blaze despite extreme weather conditions.

"We've got slightly cooler conditions today and I think everyone here in Western Australia is aware of how hot it's been the last three or four days," he said.

"[There were] really, really challenging conditions for our people on the ground who have done a really really magnificent effort … in really difficult conditions."

Superintendent Klemm said while temperatures would remain high, including a forecast maximum of 36C today trending to the low 30s until Wednesday, the end of the week looked like it would bring more relief.

Commissioner Darren Klemm (right) says cooler weather will help firefighters strengthen containment lines. ( ABC News: Emily Piesse )

"A cooler change heading into the weekend will provide opportunity for us to really shore things up up there and make sure we've got those containment lines strengthened up to the point that we can move towards getting out of this emergency warning/watch and act space and back into the advice [level]," he said.

Residents hopeful of return home

About 200 residents attended the community briefing at a temporary evacuation centre at Quinns Rocks on Monday morning.

Deputy incident controller Greg Mair told the meeting authorities were hopeful they could allow residents access to their homes later in the day.

Residents attend a community meeting in Quinns Rocks to get an update on the bushfire. ( ABC News: Frances Bell )

"We are reviewing the current emergency warning which is in Breakwater and Seatrees estates with a view of lowering those to watch and act [alerts]," he said.

"Our plan today is to be able to make that [Breakwater Drive] road safe, recheck inside the subdivision again, lower the emergency warning to a watch and act, and when we do that be able to open Breakwater Drive and allow for normal access back into that area."

He said the eastern side of the estates would still not be accessible.

He stressed that conditions could change quickly and urged people to remain vigilant and stay updated.

Another bushfire which started yesterday near the historic town of Mogumber, about 70 kilometres north-east of Yanchep, has been downgraded.