Patios, sheds and trampolines became "missiles" when a tornado smashed its way through southern Perth, authorities say.
The clean-up was continuing on Tuesday after winds in excess of 100km/h on Monday ripped roofs off houses and caused widespread blackouts, mainly around Rockingham, about 50km south of Perth.
About 50 elderly residents of the Tanby Hall hostel near Rockingham were evacuated to safety as destructive winds tore off the building's roof and water poured in about 8.30am (WST) on Monday.
No injuries were reported from the strong winds.
Fire and Emergency Services Authority (FESA) spokesman Glenn Hall said more than 40 homes in Rockingham had lost part or all of their roof.
"The problem that we've seen is that light objects such as patios and sheds and trampolines have become missiles, further exacerbating the damage," Mr Hall told the Nine Network.
FESA had received 270 calls for assistance with 213 coming from the Rockingham area.
"So, they've certainly borne the brunt of the system," Mr Hall said.
A Bureau of Meteorology spokesman said winds reached 104km/h at Ocean Reef in Perth's north, and would have been much stronger in Rockingham.
"We had at least one tornado confirmed in Rockingham, just on the damage trail from it," the spokesman said on Monday night.
Western Power said 12,000 homes were left without power, with about half of those in Rockingham.
Mr Hall said emergency crews hoped to complete their clean-up by Tuesday night.
