An emergency warning for a bushfire burning next to the Kwinana Freeway in Perth's southern suburbs has been downgraded after the blaze forced the closure of the freeway.

Key points: The fire started near the intersection of Safety Bay Road about 9:30am

The fire started near the intersection of Safety Bay Road about 9:30am The freeway between Mundijong and Karnup roads has been reopened

The freeway between Mundijong and Karnup roads has been reopened The alert has been downgraded to an advice, with no threat to lives or homes

Authorities have scaled back the warning to advice level.

The freeway was closed in both directions between Mundijong Road and Karnup Road on Thursday, but has since been reopened.

The fire started near the intersection of the Kwinana Freeway and Safety Bay Road in Baldivis.

Residents have photographed dark smoke clouds hanging over properties as the fire bears down on homes. ( Supplied: Nakira Burkala )

The Education Department says smoke was a hazard at the nearby Rivergums Primary School and Baldivis Secondary College.

Two BP service stations on either side of the Kwinana Freeway were evacuated earlier on Thursday.

Storm bearing down on coast fans flames

Authorities have grappled with four fire emergencies throughout the state, after a factory was engulfed in flames in Perth's eastern suburb of Kewdale, and two bushfire emergency warnings were triggered in the South West.

Strong, gusty and dry northerly winds ahead of a powerful storm system which is approaching WA have produced severe fire weather conditions for western parts of the state, including Perth.

"We have severe fire weather conditions with total fire bans in place," Department of Fire and Emergency Services Assistant Commissioner Brad Stringer said.

It is not common for bushfires to break out in winter, but after a dry autumn in Perth, low humidity and strong winds have exacerbated the fire danger.

"It's a combination of the soil dryness, the dryness in the vegetation, so the environment is susceptible to fire and then with the wind, when we do get a fire it can progress quite quickly," Assistant Commissioner Stringer said.

"Regrettably this is the norm of the new world where we may have multiple incidents happening on a continual basis for a long duration, with the fire season actually extending."

Rain was forecast for Perth later on Thursday, but it is not guaranteed to help extinguish the blaze.

"It depends on the volume we get and the consistency … whether it will have any effect or not," Assistant Commissioner Stringer said.

The fire has sent thick plumes of smoke billowing into the sky above Baldivis. ( Supplied: Jude Ash )

Emergency follows blaze reported on Sunday

The Baldivis blaze comes just five days after another fire forced the closure of one of the same BP service stations, a company spokeswoman told the ABC.

A fire broke out in land adjacent to the eastern service station on Sunday afternoon, she said.

The station had to be evacuated while that fire was brought under control.

The Baldivis fire was moving slowly in a south-south westerly direction late on Thursday.

It was reported at 9:30am and has burnt through about 111 hectares.

The cause of the fire is not known.