Hot weather to test WA bushfire battle

Firefighters working to contain a dangerous bushfire threatening homes and lives north of Perth are bracing for scorching, windy weather.

The Red Gully blaze, which sparked on Saturday, has burned through some 9500 hectares in the Gingin and Dandaragan shires.

Crews were able to strengthen containment lines on Thursday but remain wary of windy weather into the evening and a hot Friday when the mercury is tipped to exceed 40C.

"We're confident in some of our containment lines but there's a significant wind change coming in and that will put some pressure on," incident controller Sven Andersen told reporters.

"(We're) telling people to be aware that we're not out of the woods yet. Hotspots could spot at any time."

An emergency warning remained in place for some local communities on Thursday afternoon.

The greatest concern is held for residential estates at Ocean Farms Estate and nearby Seaview Park.

Residents whio have already left are unable to return but may be granted special access on Friday.

"If that fire breaks out, it's only an hour away from those estates," Mr Andersen said.

He said the fire could turn "quite easily" in the right conditions.

Nine national parks in the metropolitan Perth area have been temporarily closed due to severe fire danger in coming days.

"People camping or visiting WA's national parks and attractions are being reminded to remain vigilant," the state government said in a statement.

The Red Gully fire appeared under control late on Saturday but kicked up on Sunday.

There have been no reports of homes being lost, but pine plantations, olive groves and some sheds are believed to have been damaged.

Some 200 firefighters are battling the blaze with the additional help of two large air tankers from Victoria.