Two bushfires downgraded from emergency warnings in Bullsbrook and Kenwick in Perth

Two bushfires in Perth's north-east and south-eastern suburbs have been downgraded to watch and act alerts, after burning at emergency levels for hours on Thursday.

Residents in parts of Upper Swan and Bullsbrook, on the city's north-eastern fringe, have been told to monitor conditions, as have residents in parts of Kenwick, Wattle Grove, Maddington and Beckenham in the city's south-east.

Fire authorities downgraded the Kenwick blaze to watch and act about 6:45pm local time due to easing conditions, while the Bullsbrook blaze was downgraded soon after as firefighters got the fire stationary.

The Department of Fire and Emergency Services (DFES) said there remained a possible threat to lives and homes for both blazes, and that conditions could change.

The downgrade came after crews spent hours fighting the Kenwick bushfire, which sparked up just after midday.

At around 7pm local time, the DFES confirmed they had to stop aerial support at Kenwick due to an unauthorised drone being flown. 

DFES superintendent Peter Norman said no homes had been lost in the Kenwick fire.

"We can confirm one shed [was destroyed], obviously fire has come up against outbuildings and sheds, being a semi-rural area, but crews have done their best to keep them out," he said.

Superintendent Norman said the "main difficulties" were caused by resources being spread thin between separate bushfires.

"There's still parts of it there with flames probably up to 10 metres high, and still moving at least a kilometre an hour, and continuously spotting into private property," he said in the afternoon.

He warned of challenging conditions ahead with weather conditions forecast to be extreme on the weekend, and temperatures in the high 30s expected.

"I think this is our reprieve before the weekend hits. So it's going to be very important to mop this up," he said.

Perth Airport's main runway was shut for some time for safety reasons because of the amount of helitankers in the area fighting the blaze, a spokesperson said.

Four international flights were delayed, but the runway has since reopened.

The fire has burnt about 93 hectares, and it's unclear how it started.

Infernos could be seen flaring up in bushland near powerlines across the road from homes and other buildings, with fires sparking just metres away from vehicles.

Aerial support planes and helicopters flew over the area to aid firefighting efforts, contending with thick plumes of smoke blanketing the sky.

The area is a mix of semi-rural properties, suburban homes and businesses.

A number of local roads were closed, while the fire impacted traffic on Roe Highway and Tonkin Highway.

The temperature in Perth had reached 30 degrees Celsius by midday, with a high fire danger forecast.

Aerial support was sent to the fire, which was first reported at 12:12pm.

Rehoboth Christian College was evacuated, with the fire burning in the adjacent Kenwick Wetlands.

Plumes of thick smoke and walls of flame could be seen from an aerial view of the fire captured via helicopter.

'Challenging' conditions

Gusty winds and hot temperatures made for difficult firefighting conditions, with a change in wind direction expected on Thursday evening.

"We've got wind speed of around 20km per hour but they're gusting up to 50km, so pretty challenging," DFES Assistant Commissioner Danny Mosconi told ABC Radio Perth.

"At the moment the wind's coming from the south-west, but it will swing around to the east later tonight."

An evacuation centre was set up at Maddington Community Centre.

Local woman Jennie has lived in the area for 20 years.

"Standing here, it's scary," she said.

"I'm amazed to see the height of the fire.

"Have seen a couple of fires, I don't think I've ever seen it this extreme."

Second fire

Meanwhile, a second emergency warning was issued shortly after 2pm for residents in an area east of Great Northern Highway in Bullsbrook and Upper Swan, but it has also since been downgraded.

The northern edge of the bushfire is not far from RAAF Pearce, WA’s main air force base.

This fire was moving in a north-easterly direction, and lives and homes were possibly under threat, but authorities were able to get the blaze stationary by 7:15pm, warning that winds would change to a south-westerly direction around 8pm.

Bushland was charred right up to the boundary of a demolition and salvage yard, with heavy machinery seen digging containment lines right next to flames.

Aerial support was also helping to fight this fire, with helitankers having to be diverted from the Kenwick blaze.

An evacuation centre was set up at Swan Active Beechboro.

DFES confirmed the cause of the Bullsbrook blaze was accidental, caused by machinery.

At 2:26pm authorities issued a watch and act warning for a third fire, this one in the Quellington area, north of York in WA's Wheatbelt, about 100 kilometres east of Perth.

However, that fire was later downgraded and DFES said it was contained but not controlled.