Intense storms are lashing the western coast of Australia with an unusually deep low pressure system packing powerful winds and heavy rain.

The extreme weather event, typically seen only once every five years, is bringing wind gusts of up to 125 km/h to Perth and communities along Western Australia's coast.

Images of widespread destruction have flooded social media, including one showing a shed seemingly tossed into a swimming pool in Mandurah on the southwest coast.

'Act now and stay safe, with damaging to destructive winds expected this afternoon and evening,' WA's Department of Fire and Emergency Services said in an alert issued on Sunday afternoon.

'Rarely experienced winds may bring down trees, branches and powerlines and loose items or debris may become airborne.'

Electricity supplier Western Power advised more than 28,000 customers are experiencing blackouts.

Affected areas include Perth, Donnybrook, Balingup, Bunbury, Augusta, Yanchep, Langford, Ferndale, Hamilton Hill, Gosnells, and Stoneville.

As of writing, the worst of the strong winds were yet to hit. Residents in affected areas were warned to prepare to shelter by Emergency WA at 3.16pm AWST.

High tides across south-west WA were set to ease, but Bureau of Meteorology's Joey Rawson told Perth Now the most damaging winds would arrive later Sunday evening.

'These exceptionally windy conditions are unfortunately not going to go away, and they're actually going to increase as we move towards the evening,' he said.

'Places along the west coast south of Lancelin and all the way around to Albany are going to get winds strengthening.

'We could possibly see wind gusts of around 120kph to 130kph as we progress into the evening.'

Wind gusts of 117 km/h were recorded at Cape Leeuwin in the morning, while 104km/h gusts were marked at Cape Naturaliste.

The deep low pressure system brought high tides and eight-metre waves while flooding in Perth's CBD stranded cars and submerged walkways.

Devastating pictures showed boats being smashed in marinas, damaged electric wiring sparking in floodwater and flooded tides almost lapping the windows of the iconic Blue Boat House.

Residents were urged to close their curtains and remain inside away from windows as the system approached the state's southwest in the morning.

'When those strong winds are coming through, make sure you stay inside and just stay off the roads, in case of fallen power lines or trees.'

Football fans attending the West Coast Eagles versus Essendon match at Optus Stadium were also urged to plan ahead.

'This situation definitely doesn't happen every year and the wind is going to be the worst hazard,' Mr Huntington said.

A major police search earlier wrapped up when an 11-year-old autistic, non-verbal boy was found safe after going missing overnight in Perth's western suburbs during the wild weather.

The boy had been missing for almost eight hours, with police and State Emergency Service volunteers on foot and on horseback helping to locate him.

Several WA towns recorded heavy rain as the weather system moved through, with Ludlow, about 200km south of Perth, copping 43mm in two hours on Saturday night.

The cold front and low-pressure systems are expected to sweep across western parts of SA during Monday, bringing rain and wind gusts of up to 100km/h before moving across the Adelaide region later in the day.

Severe weather warnings have been issued for SA's coastal regions, the mid-north, and the southeast.