Fire crews are battling to contain a bushfire north of Perth that has triggered a second emergency warning in as many days as temperatures in the city are forecast to top 40 degrees Celsius for the next four days.

Key points: The fire has burnt 1,000 hectares and remains uncontained and uncontrolled

The fire has burnt 1,000 hectares and remains uncontained and uncontrolled Damage is being assessed after flames engulfed a service station and a house

Damage is being assessed after flames engulfed a service station and a house A second emergency warning was triggered amid heatwave conditions

As of 3:00am, people in the Perth suburb of Two Rocks and people north of Yanchep Beach Road were under immediate threat and advised to leave now, heading south along Two Rocks Road.

Anyone with homes in those areas is being told it is too dangerous to return.

A mid-afternoon wind change on Thursday saw the fire move north towards Two Rocks, threatening the suburb and houses to its east and triggering an alert.

Homes in the Seatrees and Breakwater estates were then under immediate threat, but this morning were listed as part of the watch and act area.

Anyone there planning to leave should travel east along Breakwater Drive and then take Indian Ocean Drive.

The watch and act zone now extends south of Yanchep Beach Road to Pipidinny Road in Eglinton.

Today's temperature will hit 41C in Perth with a fire danger rating of severe.

Firefighters battle the blaze which has been described as out of control and unpredictable. ( DFES: Morten Boe )

It comes after a blaze tore through Yanchep National Park and severely damaged a petrol station as well as a house on the same property late on Wednesday.

Helicopter footage from the scene showed structures on fire at the petrol station, including a number of surrounding vehicles.

Fire incident controller Andy Hinton said there were a number of Parks and Wildlife outbuildings north of Yanchep Beach Road that had also been lost.

Smoke and the orange glow from flames could be seen from homes in Yanchep. ( ABC News )

An original emergency warning was scaled back to a watch and act level shortly after 5:00am on Thursday, but Department of Fire and Emergency Services (DFES) Superintendent Ray Buchan said crews were still working hard to build containment lines to keep the fire within the national park.

"There absolutely still is a threat … we can rapidly escalate the warnings if there is a need to do that," he said.

"One service station and a house attached to it has been severely impacted by fire.

A walkway in Yanchep National Park was destroyed in the blaze. ( ABC News: Emily Piesse )

"There's been potentially some other out buildings damaged by fire … [but] we're waiting for rapid damage assessment teams to do a full assessment of the area."

Local resident Simon Evans said he and his family decided to leave until conditions improved.

"I was meant to fly out from Perth Airport this morning, but I missed the flight by two minutes because of the warnings here," he said.

"I'm glad I did miss it because it has just flared back up again, so we've come back home, got some more stuff.

Simon Evans has packed up his car and left with his family and dog Daisy. ( ABC News: James Carmody )

"At the minute, I feel lucky that it has missed our house, because it is so close to where it has come through, we just hope the wind doesn't change direction.

"The wife's packing up some sentimental [things] and I'm just packing up the hard drives and computer, all information on it."

Another resident, Tim Williams, chose to stay behind.

"The wife and kids left earlier but I think we're all right now, I think there's not much left to burn," he said.

"When it got right here it was pretty hot and goes pretty quick, there's not much you can really do.

Tim Williams has been watching the blaze from the roof of his house. ( ABC News: James Carmody )

"I just had all the sprinklers on and just kept an eye on it, it got close but I think we're all right.

"I feel sorry for anyone in the bush, they could be in trouble."

An 'icon of old Yanchep' goes up in flames

Yanchep resident Tara Annandale said conditions last night were "a bit surreal" as the fire raged and engulfed the service station.

Buildings and vehicles burn at a petrol station near Yanchep, north of Perth. ( ABC News )

"You don't really know what to do. We could see the flames and they were pretty massive," she said.

"It's so sad that such a massive part of our community was destroyed … Yanchep has grown so much and I feel like the servo was our old icon of the old Yanchep.

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

A power pole near Yanchep hangs from power lines after its base was burnt in the fire. ( ABC News: Emily Piesse )

Another resident, Kerrie France, said the blaze was much more severe than others to hit the area recently.

"We've certainly tolerated fires before and most of us are pretty used to those sort of conditions and take all precautions, but when it gets this close it's a very frightening experience," she said.

She said she had known the owners of the service station for 25 years are they were "icons in this community".

Firefighters are stationed near Yanchep homes to protect them from the blaze. ( ABC News: James Carmody )

"They've always been there for all of us … I could image they're probably in shock today and I'm just wishing them all my prayers and best," she said.

Heat means fire could change 'rapidly'

Fire authorities have said they are expecting the blaze to be a "multi-day event".

The fire is burning close to residential neighbourhoods in Yanchep. ( ABC News )

The fire has so far burnt through more than 1,680 hectares of mostly dense scrub, about 50 kilometres north of Perth's CBD, as the city braces for a run of record-breaking heat until Sunday.

More than 200 firefighters from a range of services are currently fighting the blaze and strengthening containment lines.

Fire crews have been working to construct firebreaks around the blaze. ( DFES: Morten Boe )

Superintendent Buchan said firefighters on the ground were being supported by aerial resources.

"The next three days for us are significant in relation to the 40-degree-plus days. We are mindful of the weather that's coming in with the associated wind," he said.

"We can only deal with what's presented to us on the day but our biggest concern is making sure we manage it.

"We encourage the community to maintain vigilance … although we're saying the work that's been done [so far] has been effective, due to the weather conditions that are expected, that can change rapidly."

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Parents urged to keep students at home

Two Rocks Primary School, Atlantis Beach Baptist College and Cuddles Child Care Centre in Breakwater Estate will be closed today and no-one will be allowed on-site.

The Education Department has told parents of students at those schools and centres to keep them at home.

The department has also encouraged parents of children at three other schools in the area to keep those students at home, but said a small number of staff would still be available at each of the sites to supervise children during school hours if required.

The affected schools are:

Yanchep Secondary College

Yanchep Secondary College Yanchep Lagoon Primary School

Yanchep Lagoon Primary School Yanchep Beach Primary School

Yanchep Beach Primary School Two Rocks Primary School - NO-ONE ALLOWED ON SITE

Two Rocks Primary School - NO-ONE ALLOWED ON SITE Atlantis Beach Baptist College - NO-ONE ALLOWED ON SITE

Atlantis Beach Baptist College - NO-ONE ALLOWED ON SITE Cuddles Child Care Centre in Breakwater Estate - NO-ONE ALLOWED ON SITE

The department said updates would be provided if arrangements needed to be changed on the advice of emergency service staff.

A water bomber assisting at the Yanchep bushfire takes water from a lake at a nearby golf course. ( ABC News: James Carmody )

An evacuation centre has been set up at the Gumblossom Community Centre in Quinn Rocks.

A community meeting will be held today at 10:00am at the community centre.