Search for driver missing in WA flood

The drivers of two cars found submerged in floodwaters in Western Australia have been found but a third remains missing.

A major search is underway for 34-year-old Ajit Khan, whose ute was found stranded in Piesseville in the Wheatbelt region on Tuesday.

A four-wheel drive was also found submerged nearby but the driver has since made contact with police.

Police Commissioner Chris Dawson said Mr Khan lived in Katanning and had been travelling back from Perth. He is not believed to be a strong swimmer.

A search involving police divers and State Emergency Service personnel resumed at first light in Piesseville, about 220km southeast of Perth, on Wednesday.

"We're very, very concerned ... we have a major search underway," Mr Dawson told Perth radio 6PR.

A third vehicle was found submerged in floodwaters overnight at the Murray River crossing in Hoffman, 150km southeast of Perth.

The driver has since contacted police to advise he is safe and well.

Mr Dawson urged motorists to take caution when navigating flooded roads after a cold front drenched much of the state's south.

"We just urge people do not cross, you need to find an alternative route," he said.

Perth has experienced several major storm fronts this month, recording its wettest July in 26 years.

The cold front that passed through the state's south on Monday and Tuesday left more than 21,000 homes and businesses without power.

Another is expected to arrive on Thursday, potentially causing rivers to flood in the Perth Hills and the southwest.