More than 100 firefighters are battling the blaze that is believed to have damaged three homes and forced hundreds of local families to evacuate their properties overnight.
An emergency warning remains in place for Wanneroo, Jandabup, Mariginiup, Melaleuca, Sinagra and Tapping, about 30km north of the city centre.
Some residents have been told it is too late to leave their homes and they should immediately find shelter away from the fire front that is moving in a southwesterly direction.
Western Australia is currently in the grips of a severe heatwave and Perth is forecast to reach 40C on Thursday, with wind gusts up to 80 km/h.
More than 1,000 properties in the bushfire area are without power, and an evacuation centre has been set up in the nearby suburb of Quinns Rock.
Local resident Bruno Rikli helped evacuate an elderly couple from home overnight as the firefront crept within a few streets of their property.Â
"There was a massive plume of smoke in the night sky and a ball of red embers that was glowing red," he told AAP.
"Roads were blocked but we got them out."
Mr Rikli said the couple's home survived the night without damage but the wind had started to whip up on Thursday morning, with ash falling on homes several kilometres west of the blaze.
"You can smell the smoke and it's hazy but fire crews are doing an amazing job," he said.
The fire was reported about 1pm on Wednesday and 15 sq/km of bush and grassland has been burned.
Bushfire
27°C