The massive blaze with an 80km perimeter raged through the night near the hills town of Wooroloo before moving west onto the city's coastal plain where it is threatening homes in northern suburbs.

Weather conditions are expected to worsen overnight with wind gusts of up to 75km/h possible, with a smoke alert issued for the entire Perth metropolitan area.

Western Australia's Fire and Emergency Services Commissioner Darren Klemm says it's likely the number of homes lost will climb.

"Firefighters have done a remarkable job in some of the most challenging conditions that we've experienced in the metropolitan region for some time," he said.

"Tragically, 59 properties have been lost in this fire, and that number may increase as we continue to assess the extent of the damage.

"This will be devastating news for the owners and occupiers of these homes, and our thoughts are with them."

He said crews had faced "a difficult and incredibly fast-moving" blaze that was spotting 3.5km ahead of the fire front at its height last night.

"Firefighters were just going from one house to the next trying to save them," he said.

"We are still in really difficult conditions. There is a lot of work to be done on the fire to make it safe and we are a long way from that point."

Earlier, Premier Mark McGowan said firefighters would continue to check destroyed homes in the rural suburb of Tilden Park to check if any lives had been lost.

He said a large aerial tanker was en route from NSW to help battle the blaze and the prime minister had been briefed on the situation.

"This is an extremely dangerous fire and a serious situation. Weather conditions are extremely volatile," the premier said.

"Please do everything you can to keep you and your family safe and look after each other."

Meanwhile, people in Perth's CBD and coastal suburbs have reported ash landing at their homes, up to 35km from the blaze.

Operations at RAAF Base Pearce - which is in the path of the fire - have been suspended and preparations are being made to evacuate.

DFES Deputy Commissioner Craig Waters said the fire had doubled in size overnight and burned through more than 8000 hectares.

"Strong winds are hampering us getting in and containing the fire and bringing it under control," he said.

Six firefighters have received minor injuries.

People in a 25km stretch west from Wooroloo to the Walyunga National Park northeast of Perth have been told it is too late to leave.

"You must shelter before the fire arrives, as the extreme heat will kill you well before the flames reach you," the latest DFES warning said.

Jenni Stanton, 59, received a text about 2am telling her to evacuate from her home at The Vines, about a kilometre from the blaze.

But she and her husband decided to stay put, saying the roads out of the semi-rural suburb were bumper-to-bumper with traffic.

"The fire has jumped the Great Northern Highway west of Walyunga, so it's closer to us now," she told AAP mid-morning.

"The yard is covered in ash and we can hear the water bombers."

Neighbour Melissa Stahl, 49, received the same text.

"I could smell the fire and went out the back and the whole yard was filled with smoke," she said.

"My husband Michael said we better go.

"We grabbed bedding, photos, the two kids and the dog and got out of there."

Residents in the surrounding areas, including Parkerville, Ellenbrook, Chidlow and Jane Brook, have been told to leave if they are not prepared to fight the blaze.

Evacuation centres have been set up at the Brown Park Recreation Complex in Swan View, Swan Active in Midland and Swan Active in Beechboro.

Australian Associated Press