Firefighters in Perth have welcomed daylight as they work to contain a bushfire that has destroyed at least 41 homes.

It was a long night for more than 100 firefighters battling the out-of-control blaze at Roleystone, south-east of Perth, which has burnt through 500 hectares.

The fire broke out when a spark from an angle grinder ignited dry grass, forcing hundreds to flee their homes as 70 kilometre-per-hour winds whipped flames straight onto their properties.

Fire crews hope there is some relief ahead, as the strong winds are expected to ease this afternoon. The morning light has also allowed helicopters to rejoin the firefighting effort.

Fire and Emergency Services Authority (FESA) spokesman Allen Gale says it will be a challenging day for fire crews.

"We've got downed powerlines and poles and we've also got trees - if they haven't fallen already they're threatening to fall, so moving around in the area is very dangerous," he said.

Homes in Kelmscott and Roleystone remain under threat and at least 60 structures have been damaged.

People in the path of the fire spent the night with family or at an evacuation point at Armadale Arena.

They do not know if their homes are still standing, but the extent of the damage should become clear as the day goes on.

"There is not a lot of information coming in at the moment," one resident said.

"They have told us there will be a briefing [this] morning so everyone has their fingers crossed."

Corey Marshall evacuated his wife and four children as soon as he heard the bushfire warnings rather than stay and defend his home.

"There wasn't much to it. We just really grabbed a few minor possessions and clothes and threw the kids in the car and came here," he said.

"As we said, everything else can be replaced."

Meanwhile, parts of an area north-east of Perth, where a second large blaze is burning, have been downgraded to a watch-and-act warning.

But FESA spokesman Craig Hynes says one firefighter at Roleystone was injured fighting the massive blaze.

"No lives have been lost and injuries are at a minimum, apart from one volunteer firefighter who was hospitalised," he said.

Resident Lionel Goodall says he felt like he had to stay with his house for as long as he could.

"It was on our back doorstep and it didn't take very long at all [to get there] so it must have jumped the highway and come through the back," he said.

"I went outside and all the backyard is gone. It is all just black and smoke and the fences are alight, so I just got my hose out and started putting all the fires out in my yard and my neighbour's as well to stop them from spreading.

"Once I put all the fire out it took about an hour of double-checking and triple-checking everything.

"I've just been running around now waiting and seeing what is going to happen."

Meanwhile, about 100 firefighters are still working to contain an out-of-control blaze that is threatening homes in Perth's north-east.

The fire at Red Hill has burnt more than 1,100 hectares since it started on Saturday night.

No homes have been damaged so far.

Fires are also burning in Chittering, 50 kilometres north of Perth, and Jarrahdale, 60 kilometres south-east of the city.

There is no threat to lives or homes but residents in the areas are urged to stay alert.