Tens of thousands of homes are without power and emergency services have received hundreds of calls for assistance after a series of powerful storms tore through the southern half of Western Australia over the weekend.

Flooding and damaging winds on Saturday night were followed by a second wild storm on Sunday evening, disrupting plans across the WA Day long weekend and causing some flights into Perth Airport to be diverted.

Cyclone-strength winds were recorded in some areas, including Cape Naturaliste where there was a gust of 135 kilometres per hour.

An apartment building in the coastal Perth suburb of Cottesloe had its roof torn off, damaging nearby properties, the Department of Fire and Emergency Services (DFES) confirmed.

Part of a gutter from a roof lies on grass next to a white apartment building.

Parts of the apartment building’s roof were left strewn around the property. (ABC News: Jasmine Hughes)

Residents near the Hawkstone Street apartments have been warned to stay indoors, with authorities warning of the risk of roofing materials and debris from the site becoming airborne in strong winds.

Storm warnings remain current across a large swathe of the state, from the Mid West Gascoyne through to the Great Southern, and including the Perth metropolitan area.

Tree falls on car amid wild WA weather

Two people have had a lucky escape after a tree fell onto their car on a major highway in WA’s South West, as strong winds lashed the region.

DFES said despite the storms easing, conditions remained hazardous and people should stay away from damaged buildings, fallen trees and powerlines.

Rainfall in Perth eased overnight, with only 4 millimetres recorded.

But the western end of Riverside Drive in Perth’s CBD has been closed due to flooding.

Enormous task to restore power

Western Power is working to restore power to 69,000 customers who have been cut off across WA, with more than 250 storm-related outages in the South West.

Western Power estimated most outages would be resolved by around 6:30pm but said the restoration effort would be an enormous task.

A fallen powerline

Strong winds have brought down power poles and lines, including in the Perth suburb of Beaconsfield. (Facebook: Sandy Armstrong)

“There are about 1,300 incidents we’ve got on the network at the moment, so it’s definitely not a small event,” Western Power’s head of operational maintenance Brett Hovingh said.

The State Emergency Service has also received nearly 700 requests for help.

There are reports of fallen trees, power lines and debris on the roads across Perth and the southern and western coastlines, and Main Roads is urging motorists to drive with caution.

Fremantle’s WA Day festival has been cancelled due to a forecast of continued strong winds in the metropolitan area on Monday.

Port Beach, which has been progressively eroded in recent decades, appears to have suffered further erosion in the storms, with wire fencing that had been installed to protect sand banks ripped up.

Sand banks at Port Beach in Perth left eroded after a storm, with mesh installed to reduce erosion hanging down.

High tides brought by the severe weather have caused further erosion at Port Beach. (ABC News: Jasmine Hughes)

Damage assessed, flights diverted

While Sunday night’s storm hit Busselton and surrounding communities with near record-breaking winds, the city and wider region appear to have escaped major damage.

The wind and rain toppled trees and left debris strewn across roads, with long weekend travellers urged to be cautious as they make the trip home to Perth.

But initial reports indicated no serious damage to homes or major infrastructure.

A large tree lies over the side fence of a residentual property next to a road after it was brought down in a storm.

A large tree was left laying on a fence at one property in Busselton on Monday. (ABC News: Neve Brissenden)

Four flights had to be diverted to Kalgoorlie-Boulder Airport overnight because of strong winds at Perth Airport.

A Virgin flight from Karratha made two failed attempts to land at Perth before being diverted, as did a TransNusa Aviation flight from Denpasar.

The TransNusa passengers were not allowed off their aircraft during the delay as Kalgoorlie-Boulder Airport does not have customs facilities. 

Two Qantas flights, one from Sydney and another from Brisbane, were diverted directly to Kalgoorlie-Boulder Airport before eventually landing in Perth. 

Winds reach cyclone strength

Bureau of Meteorology (BOM) duty forecaster Jess Lingard said the 135km/h wind gust recorded at Cape Naturaliste was a May wind speed record for the area.

“That is pushing into category 2 cyclone strength, so very, very strong winds,” she told 102.5 ABC Radio Perth.

“[Winds] have calmed down a little bit now, and as such the warning area looks a little bit different today.”

A severe weather warning remains in place for people in Eucla and parts of South East Coastal districts.

Men in orange uniform removing trees from a road.

State Emergency Service crews were called out to Rivervale in Perth after trees were brought down. (ABC News: Lauren Smith)

The BOM said an intense low-pressure system was moving east along the southern coast, bringing damaging wind gusts up to 90km/h, with winds expected to ease on Monday night.

A coastal hazard warning has also been issued for an area from Windy Harbour to Israelite Bay, with seafarers advised to be wary of abnormally high tides.