Western Australia storm
© JMA/Himawari-8, RAMMB/CIRA
Western Australia was hit by its worst storm in a decade on Sunday, leaving about 50,000 homes and businesses without power as the weather bureau recorded wind of up to 130kph.

Up to 100 millimetres of rain is expected to fall along the west coast, while tides are predicted to swell before reaching a peak of 8 metres on Monday.

The storm was caused by the remnants of a tropical cyclone meeting a cold front, and emergency services have warned of flooding and dangerous seas.

Officials said conditions were expected to worsen overnight as the severe storm progressed.

The acting assistant commissioner of Western Australia's department of fire and emergency services called the storm "a once-in-a-decade-type system".

James Ashley, of the weather bureau, said the formation was dynamic and complex, as a system from Cyclone Mangga in the southern Indian Ocean interacted with the cold front.

"It's affecting a large area. Normally, at this time of the year we're just concentrating on severe weather with cold fronts across south-west WA," Mr Ashley said.

"With the tropical interaction, it's meaning that north-western parts of the state are being affected, and it's going to produce rainfall right through into the Kimberley (region) as well.

"So pretty much the whole of WA will be affected by this system, which makes it really quite unusual."

A power company said some households should expect to remain without electricity overnight, particularly in places where it was not safe for crews to repair the network.

The worst of the weather was due to hit Perth later on Sunday evening and Monday morning, and not ease until Monday afternoon.

There were reports of damage to buildings, homes, fences, electricity infrastructure and trees across Perth as the storm front moved south.