Severe thunderstorms are forecast for Perth suburbs and the southern corner of the state today, potentially causing flash flooding in some areas.
The Department of Fire and Emergency Services issued the alert about 8.30am after a severe thunderstorm overnight dumped more than 70mm of rain on Rockingham and Mandurah, south of Perth.
Lightning strikes from that storm cut power to 4000 homes and power has been restored to more than a quarter of those, utility Western Power said.
The latest warning applies to the area between Lancelin, about 110km north of Perth, to Lake King in the Eastern Wheatbelt region, to Windy Harbour on the south coast between Walpole and Augusta.
The DFES said people in this area - including Perth, Mandurah, York, Narrogin, Bunbury, Busselton, Katanning, Margaret River and Bridgetown - should take action to keep themselves and homes safe.
"Very heavy rainfall, which may lead to flash flooding with once in 50 year rainfall intensities, has been observed in the areas between Mandurah and Harvey," the DFES said.
"Storms may be accompanied by damaging winds."
The DFES warned the storms could damage homes and make travel dangerous.
