Emergency services are assessing the damage from a storm over the southern half of the state overnight.
The State Emergency Service received more than 130 calls for help, mainly for roof damage, uprooted trees and flooding.
The Bureau of Meteorology says wind gusts of up to 110 kilometres an hour were recorded along the coast.
Perth recorded almost 13 millimetres of rain and Bickley almost 23.
A wall partially collapsed at a block of units in Clydesdale Street, Como.
Santidiago Arevalo was inside one of the units at the time when he heard what sounded like a loud clap of thunder.
"We were watching movie last night and we heard a loud bang like an explosion or a loud thunder," he said.
"It's really unbelievable that because of that heavy rain and the wind, the strong wind, yeah it fell down."
Mr Arevalo says it was lucky the strong wind subsided.
"If the strong wind and rain came again those residents would have been affected and it would have blown away the roof," he said.
Trees have fallen on houses in Thornlie and Wanneroo as well as on an enclosure at the Armadale Reptile and Wildlife Centre.
And the Baptist College in Mandurah has lost part of its Library roof.
The duty forecaster says the worst of the storm is over for Perth and conditions should moderate during the day.
The storm caused widespread power blackouts.
Western Power says crews have been working through the night to restore electricity to 5,500 customers.
In the south-west town of Pemberton, almost 1,000 customers are without power.
The worst affected suburbs in Perth are Nollamara, Westminster and Hamilton Hill.
Boats have also washed up on shore after breaking their moorings at Rockingham and Jervoise Bay.
© ABC 2013
11:39 EDT El Nino is one extreme of the El Nino-Southern Oscillation (ENSO) phenomena, in which La Nina is its counterpart.