A storm has pummelled Western Australia, sending trampolines and sheds flying and causing flash flooding and power cuts.

And the Bureau of Meteorology warns the weather is set to turn even worse.

In Mandurah, south of Perth, a neighbour's shed was sent crashing into a family's backyard pool.

READ MORE: 'I was definitely dying': Tradie relives horror road rage attack

A jetty in Safety Bay is submerged as heavy weather hits the state. Michael Philipps

"It came over that side, over the fence, and then the next thing we know we got a free home," the owner said.

Down the road, Dawn Crawford was holding on, battling the wind to stop her fence from giving way.

"I was here holding this for an hour," she said.

Flash flooding forced Perth locals to get creative for a morning coffee.

"We've had jellyfish, we've had ducks, and then we've had our regulars, which is great," joked Rob Strahan from Bayswater Oarhouse.

READ MORE: Man accused of stalking Norwegian princess studying in Sydney

Wild weather has caused flooding of roads in Applecross. Cameron Myles

High swells in Hillarys became a playground for surfers.

Some boats sank as the Swan River spilled over its banks.

SES crews were kept busy responding to more than 380 calls for help since 5pm on Saturday.

Power lines came down across multiple suburbs, with more than 28,000 Western Power customers without power.

"I was in bed and the kids come running in and screaming the power's out so wasn't too happy. Wanted to be able to watch the footy this afternoon," Beaconsfield man Steve Tonge said.

Fans make their way through the weather into Optus Stadium for the Eagles and Bombers clash.  AFL Photos via Getty Images

A tree smashed a roof narrowly missing Brad Counsel and his dog.

"Gust of wind and then down came the tree," he said.

The storm has already dumped more than 57.4 millimetres of rain in Capel, between Bunbury and Busselton, in the past 24 hours.

Cape Leeuwin, the most south-westerly point of the mainland, recorded wind gusts of 122km/h.

Emergency crews called for everyone in the state's south-east to tie down loose items before the full force hit.

Joey Rawson from the Bureau of Meteorology said the wild weather would be unusual.

A once-in-five-year storm is due to hit Perth in coming hours, with heavy rain already drenching parts of Western Australia. Bureau of Meteorology

"As we progress into the evening this low pressure system really intensifies and it's going to bring conditions that we don't see that often in south-west WA."

Earlier forecasts even predicted the risk of tornadoes.

The wild weather could also hit other states this week.