Pole-top fires, sparked by heat and rain, cut power to 40,000 WA homes and businesses

Downed powerlines have sparked danger across Perth, plunging entire suburbs into darkness.

Fire crews say wet weather, mixed with heatwave temperatures and dust triggered the widespread outages as emergency services raced to restore power.

Pole-top fires wreaked havoc on the power grid, blacking out traffic lights and leaving local businesses out of pocket.

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Gregory Assenov from Harvest Boulangerie Patisserie said they were forced to scrap thousands of dollars worth of fresh produce.

"It's a big loss, it's definitely a five-figure loss for us," he told 9News.

"Unfortunately, we've had to stop all the production and call it a day and just throw all the stock that we have."

Residents in the south were also left in limbo.

"It's pretty annoying," Holly Tickner told 9News. "I have about $18,000 worth of medication in my fridge that I need."

Across the south-west 100 pole-top fires plunged 38,000 homes and businesses into darkness.

Authorities blame light rain combined with heatwave temperatures and dust build-up.

"Often these things can be resolved very quickly, it's often just the quantum of them that causes the issue," Darren Klemm of the Department of Fire and Emergency Services said.

Scarborough was the worst-affected area, with power out all Friday night and locals describing it as a ghost town.

Western Power crews worked around the clock yesterday to restore it.

"Western Power are investigating new technology like drones to allow them to apply silicone coatings in a live electricity environment," WA Premier Roger Cook said.

The heat also raised bushfires to emergency levels across WA, with a historic family home among the four destroyed by flames.

Despite the heroic efforts of a father and son, who tried to fight the flames, their beloved Wheatbelt estate property of more than 100 years was reduced to rubble.

"My dad had lived there for 70 years - it's my dad's 70th bday tomorrow, he was born and raised at that house with his mother and father and from memory there was his grandfather who lived in that house also," family member Samantha Spurr told 9News.

Located 200 kilometres south-east of Perth, in Arthur River, the home was helpless against the fire.

"My brother pretty much grabbed my dad and they went and grabbed the fire unit but there were 50-kilometre winds, so the fire was roaring so fast it pretty much came to the farm before they could stop anything," Spurr added.

The farm's stable is still standing but sheds, clothes and cherished photos are just some of what Samantha Spurr's parents have lost.

"They're currently in a room with my brother because they have nowhere to go."

An online fundraiser has been organised to help the Spurr family.

In total, three homes were destroyed in Arthur River and a fourth lost in a bushfire near Narrikup further south.

"We got up to five emergency warning level bushfires over course of [Friday] afternoon as parts east of Perth dealt with difficult conditions," Klemm said.