Fire crews will work through the night to control a blaze in the shire of Gingin, north of Perth.

The fire started on Thursday morning and has burnt through more than 2,000 hectares.

An emergency warning has been downgraded to a watch and act due to lighter winds and rising humidity levels, but the fire is still out of control.

The area affected is bounded by Teatree Road, Mooliabeenee Road, Crest Hill Road, Great Northern Highway to Ioppolo Road, to Brennan Road in Bindoon and Upper Chittering.

Earlier the fire, which had flames of 20 metres high, was burning directly towards the township of Bindoon and homes were under threat.

Emergency authorities are warning that properties on the eastern flank of the fire are still under threat.

Emergency services say no homes have been lost yet, but residents in the path of the fire are being urged to leave now or prepare to defend.

About 100 people have turned up at an evacuation centre in Muchea.

The Education Department has advised that the Bindoon Primary school will be closed on Friday.

Meanwhile another fire is threatening homes in Perth's south-east.

The fire is burning on both sides of the Tonkin Highway at Armadale.

Allen Gale from the Department of Fire and Emergency Services is urging people to either leave, or get ready to actively defend their homes.

"There's a couple of properties there that are possibly going to be threatened, we've upgraded it to a watch and act, so it's time now for people to take action, you don't wait," he said.