A bushfire threatening lives and homes in Perth's north has remained at emergency level for a fourth consecutive day — and it may stay there for several more, with flames being fanned further up the coast.

Key points: The fire has burnt through 12,000 hectares, destroying several structures

The fire has burnt through 12,000 hectares, destroying several structures DFES' commissioner says difficult times are ahead and warns of further damage

DFES' commissioner says difficult times are ahead and warns of further damage Authorities say they don't believe arson is to blame for the fire

Hundreds of firefighters battling the blaze were able to slow its spread on Friday night but they spent Saturday dealing with changes in wind direction and another day of blistering heat.

The emergency warning is in place for a 45-kilometre stretch of coast including the towns of Guilderton, Seabird and parts of Two Rocks.

The smaller communities of Woodridge, Caraban, Gabbadah, Neergabby, Wilbinga, Yeal, Redfield Park, Sovereign Hill, the Seatrees and Breakwater estates and parts of Beermullah, Muckenburra, Wanerie, Neergabby and Yanchep remained in the the emergency warning zone on Sunday morning.

Fire danger has been declared for the metropolitan region, the Pilbara, Goldfields Midlands, the Great Southern, the mid-west Gascoyne, as well as the south-west and lower south-west of the state.

Areas at advice level include Palmer in the Shire of Collie.

In the Shire of Dardanup there is a watch and act warning in place for for Honeymoon Pool Campground and Stones Brook Campground in Wellington National Park.

In the same region, an area bounded by Coalfields Highway, Mungalup Road and Wellington Dam in Wellington National Park is at advice level.

It is now safe for people in Seatrees and Breakwater estates to leave in a westerly direction towards Two Rocks.

Residents of Seatrees Estate, north of Breakwater Drive, can now apply for a permit which allows them to return to their homes for one hour, plus driving time.

An alert posted at 8:30pm on Saturday advised people in Guilderton and Woodridge to leave in an easterly direction towards Indian Ocean Drive and use Gingin Brook Road to travel towards Gingin.

A later alert said firefighters would conduct controlled, hazard reduction burns south of Woodridge during the night.

About 400 firefighters were attending the scene, with Emergency WA estimating crews had saved more than 6,000 homes in the area.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 28 seconds 1 m 28 s Helicopter vision from Saturday morning shows bushland on fire within Breakwater Estate.

An evacuation centre was set up at Granville Civic Centre in Weld Street, Gingin.

Woodridge residents lost access to scheme water at 6:00pm on Saturday.

A watch and act warning extends north to the coastal town of Ledge Point and south to Yanchep and Eglinton.

One home, a petrol station and some buildings associated with Yanchep National Park were lost when the bushfire started on Wednesday but since then no other homes have been lost.

'We've got difficult times ahead': commissioner

Fire and Emergency Services commissioner Darren Klemm said firefighters were continuing to face very difficult conditions.

WA's Fire and Emergency commissioner Darren Klemm warned damage caused by the fire could escalate. ( ABC News )

"The fire is moving at a rapid rate to the north-east and as you've seen with the wind conditions we've got here today, it's going to be difficult for us to pull that fire up before we get into nightfall tonight," he said.

"We've continued to put containment lines around massive areas of this fire, but we are dealing with really, really difficult conditions and we've consistently seen those containment lines being breached.

"We've got some difficult times ahead of us — today and tomorrow are going to be particularly challenging and people need to be aware that things could escalate from here in terms of the damage."



Fire will burn for days

Department of Fire and Emergency Services (DFES) superintendent Gary Baxter said the fire could burn for more than a week.

"I don't suspect that we're going to extinguish it anytime in the next week or so but certainly we'll try and get containment lines strengthened," he said.

"Controlling it is a different thing but containing it over the next few days is an objective you'd hope in the next couple of weeks to fully extinguish the fire.

"That's to completely extinguish 100 per cent of the fire ground — that's a complete blackout — so that over the next few weeks and into the next couple of months of over summer we don't have to revisit the same patch."

Yanchep residents watch on as flames move close to their streets. ( ABC News: James Carmody )

Superintendent Baxter said the area was a popular holiday destination and some people were not taking the warnings seriously.

"We had people fishing along the beach yesterday," he said.

"We have asked people not to go there, to evacuate out of the area but unfortunately some people don't think that their safety is as paramount as we do."

Weary firefighters 'battling like Trojans'

DFES superintendent Andrew Hinton said the blaze was taking a toll on firefighters.

"I have no doubt that they are fatigued, I have no doubt despite our best efforts to continue to hydrate and feed them that they are weary, and slightly vulnerable themselves, but they are battling like Trojans," he said.

"We're in day four of five 41-degree days … it's only going down to about 25, 26 overnight, and the wind is continuing to push in from the deserts on the easterlies.

"We're not getting any respite. It's fatiguing."

No relief from blistering heat

The fire has been fuelled by heatwave conditions that saw temperatures in the city top 40 degrees Celsius on Friday and Saturday, with similar conditions expected for Sunday.

The blaze has so far burnt through close to 12,000 hectares of bushland, tearing through the Yanchep National Park.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 3 minutes 52 seconds 3 m 52 s Yanchep fire seen from the air

The Bureau of Meteorology's Steph Bond said winds were not forecast to be as strong as previous days.

"But what is still a bit worrisome is the amount of wind direction changes we have today," she said.

A map showing fires burning in the past 12 hours in the Yanchep area. ( Supplied: Landgate )

"Just because winds have eased, it doesn't mean the danger has stopped at all, and we still have that hot day tomorrow as well."

DFES superintendent Andrew Hinton said the coastal terrain had made the firefighting effort very difficult.

"Some appliances got bogged last night, it's very difficult in the sand dunes," he said.

"It's tricky country, it's as tricky as we get here."

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

Two Rocks resident Lyn Ward said it was scary to watch flames come so close to her neighbourhood.

"The house, everything stinks of smoke. It's really uncomfortable at the moment," he said.

"I tell you what, those firies, they deserve every penny they earn, they're amazing — they've saved everything.

Two Rocks resident Lyn Ward said she's very grateful to the firefighters who have saved homes in her town. ( ABC News: Nicolas Perpitch )

"These poor guys are worn out now. I don't know how the guys over east have been doing for weeks and weeks on end."

'Who gives a brass razoo what's in the house?'

More than 30 residents have taken shelter at the Gumblossom Community Centre in Quinns Rocks, while a second evacuation centre has been set up at the Granville Civic Centre in Gingin.

The fire forced Dale Kelleher, her two dogs and her cat to evacuate from Sovereign Hill on Friday afternoon.

"The smoke just suddenly came over," Ms Kelleher said.

"My mobile [rang] and my friends from Safety Bay said 'what are you doing there, woman, get to Gingin', so in less than 45 minutes the dogs and my 17-year-old cat [were in the car].

"I slept in the car last night, with the cat next to me and the two boys in the back, but tonight they're going to give me a folder bed out the back."

Dale Kelleher and her animals including 14-year-old dog Red are staying at the Gingin evacuation centre. ( ABC News: James Carmody )

Ms Kelleher said she disagreed with the decision by some Sovereign Hill residents to stay and defend their properties.

"If an old chook like me can get out, with two ageing dogs and a cat, in 45 minutes … And who gives a brass razoo what's in the house? What do you value most? They're my fur babies so I'm out just like that," she said.

"Once you're evacuated, they said you cannot re-enter, despite a few people saying you can sweet-talk your way in."

About 200 people from affected areas gathered for a community meeting in Gingin on Saturday afternoon.

Brad Stringer took to the air to get a look at the blaze. ( ABC News: James Carmody )

DFES assistant commissioner Brad Stringer addressed the crowd after going up in a helicopter to view the fire.

Mr Stringer said he had seen the blaze burning about 1 kilometre from Guilderton and not far from Woodridge.

He said firefighters were on the ground in both of those locations and containment lines were being built.

But the sea breeze had seen some of those containment lines fail.

Utility services have been affected by the fire with several hundred properties without power, telephone services down in the Two Rocks area and bore fields supplying water to Two Rocks compromised.

Thirty-four people spent Thursday night at the Quinns Rock evacuation centre. ( ABC News: Ben Gubana )

Western Power said people in Seatrees and Breakwater Estates will not have power restored until at least Sunday.

Yanchep National Park and the Wilbinga Conservation Park remains closed.

There was a total fire ban across the Perth metropolitan area on Saturday.

The Red Cross has established a hotline number for people affected by the fire to get in touch with family and friends; 1800 351 375