An emergency warning has been downgraded for a bushfire that had been threatening lives and homes in the northern Perth suburb of Yanchep.

The alert was scaled back to a watch and act level shortly after 5am this morning, after a petrol station as well as a house on the same property were damaged by the fire late yesterday.

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

Almost 120 firefighters and four water bombers are working to extinguish the blaze, which is now stationary in Yanchep National Park but has not been contained or controlled.

The fire has burnt through about 700 hectares of dense scrub, about 50 kilometres north of the Perth CBD, as the city braces for a run of record-breaking heat until Sunday.

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

The watch and act warning covers parts of Two Rocks, Eglinton and Yanchep in the City of Wanneroo, with authorities saying there was still a possible threat to lives and homes and conditions were changing.

Fire 'still a threat' as heatwave looms

Department of Fire and Emergency Services (DFES) superintendent Ray Buchan said crews were working to build containment lines to keep the fire in the national park.

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

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

"So although it is not fully controlled or contained, we've reduced the warnings to reduce the anxiety associated with constant messages going out with emergency warnings.

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

"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."

Police wear face masks as they control a roadblock in Yanchep. ( ABC News: James Carmody )

Superintendent Buchan said firefighters on the ground would be supported by aerial resources today.

"The next three days for us are significant in relation to the 40C-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 over the last 18 hours has been effective, due to the weather conditions that are expected, that can change rapidly."

Almost 1,400 homes close to the fireground were without power at one point.

Residents flee, roads closed

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

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

Yanchep resident Marvin "Zippy" Harper said he evacuated his home as soon as he saw flames close to his street.

"We heard a loud bang — I don't know whether that was the petrol station going up — then next minute, you know the fire was coming quicker and quicker so we had to get out," he said.

"It was bigger than the trees, some of the flames. It was pretty bad."

Yanchep resident Marvin 'Zippy' Harper is sons Dewi (L) and Dylan (R) evacuated their home as soon as they saw flames. ( ABC News: James Carmody )

Anita McInnes evacuated her home in Yanchep to stay with family for the night.

"When it first started there was the strongest smell. When I opened my front door it was just like the bushfire was right in my yard, that's how strong it was," she said.

Three major roads in the area have been shut including a 13-kilometre stretch of Indian Ocean Drive from Breakwater Drive to Pipidinny Road.

The fire has engulfed part of a property on Yanchep Beach Road. ( ABC News )

Yanchep Beach Road and Old Yanchep Beach Road have also been closed along with Yanchep National Park.

The watch and act alert affects people bounded by the town of Two Rocks to the north, Yanchep National Park to the east, Eglinton to the south and Two Rocks Road and Marmion Road to the west in the City of Wanneroo.

That includes much of the Yanchep town site between Yanchep Beach Road and Brazier Road.

A fire front burns through part of the Yanchep National Park. ( ABC News )

A bushfire advice is in place for the northern part of Two Rocks, including Seatrees Estates, and the eastern part of Yanchep.

The cause of the fire is unknown.

Toodyay bushfire emergency

Meanwhile, an earlier emergency warning has been downgraded for a fire burning near the town of Toodyay, about 80 kilometres north-east of Perth.

A bushfire advice remains in place for people south of Folewood Road, east of Sandplain Road, and north and west of Toodyay Road, including Majestic Height and Majestic Waters.

Fire tore through properties near the north-east Perth town of Toodyay. ( Supplied: Chris Wood )

The fire is stationary and has been contained and controlled after burning through 15 hectares.

Toodyay resident and volunteer firefighter Chris Wood said flames tore through the local golf course.

"Someone's been whipper snipping, tidying up around a house and there's been a spark of some description which has lit up a fire and off she went," he said.

The fire broke out in the same area where 38 homes were destroyed in a fire in 2009.