Widespread heavy rain has caused minor flooding north of Perth.
Falls up to 15 mm overnight to Saturday resulted in both the Swan River at Walyunga and the Avon River swelling, authorities say.
Similar totals are forecast for the remainder of the weekend, with renewed flooding and sharp increases in river levels possible.
The Bureau of Meteorology on Saturday advised a strong cold front would move over the southwest of the state by late evening, resulting in an increase in showers, thunderstorms and damaging winds.
A cold and unstable air mass will follow during Sunday with brief but heavy showers and thunderstorms.
Wind gusts up to 110 km/h that could cause damage to homes and property are expected to initially develop southwest of Cape Naturaliste to Windy Harbour after 8pm local time on Saturday.
They will then extend to southwest of Mandurah to Bremer Bay by midnight.
The conditions are expected to be widespread about coastal areas extending from Jurien Bay to Albany and throughout the South West district.
Ongoing damaging surf conditions which could cause significant beach erosion will continue between Shark Bay and Esperance.
Catchments saturated by recent storms combined with areas of flooding may adversely affect road conditions along the Swan River, authorities said.
Levels on Saturday morning were 3.79 metres and steady but likely to remain above the minor flood level of 3.50 m during the day.
Emergency services said the river was likely to peak near 4.10 metres Sunday afternoon.
Residents were warned flooding was possible and to be prepared to relocate equipment and livestock.
People in the Murray River catchment downstream of Pinjarra should also take care following rising water levels in local rivers and streams.
The same advice was issued for residents in parts of the Goldfields-Midlands.
Australian Associated Press