A tornado has formed in a severe storm that damaged several homes and businesses in the Perth metropolitan area.
The storm front tore roofs off houses, and uprooted trees and power lines.
The southern suburbs of Hilton and O'Connor, as well as Claremont, received the brunt of the damage.
The Bureau of Meteorology said the conditions had resulted in a tornado forming in the suburb of O'Connor.
Western Power spokesman Brad Lacey said at the peak 12,000 homes were without power.
"Our crews are working through some trying conditions but we're managing to get people up and running, and we're hoping by the end of the day to have most people restored," he said.
"We've got wires on the ground due to trees falling, we've got parts of roofs sitting on lines, we've got poles which have been broken ... but we're confident we'll have everything back by this afternoon."
About 1,000 customers were still waiting for power to be reconnected about 4:00pm (AWST).
The weather bureau recorded wind gusts of more than 85 kilometres per hour in Perth, and winds of up to 120 kilometres an hour in Yallingup.
Steve Howarth said the storm ripped part of the roof off his Hilton home, exposing electrical wires.
"It was already windy and rainy, then there was an almighty bang and we're staring up at the rain," he said.
"A huge green flash, the power cables came down, then you could hear a pick up in the noise outside and it's just chaos.
"There's trees coming down, metal sheeting flying around, lots of banging. Incredible.
"We've lost a large portion of the roof, we've lost the front apex of the garage, the garage door was smashed in, there was debris flying around, tiles, metal sheeting, the warehouse, just about everything.
"The only thing intact were the windows."
About 1,000 properties were also without power in WA's South West during the storms.
Most of those affected were in Northcliffe, where 450 homes lost power.
© ABC 2014
17:37 EDT Much of western New South Wales has begun a heat wave, reaching at least five degrees above average for at least five days, averaging a maximum of 35 degrees or more.