Parts of WA hit by thunderstorms, floods

Severe thunderstorms are set to hit Perth and surrounding regions, with flooding already affecting the state's southwest.

People in the Perth Metropolitan, Great Southern, South West, Lower South West and Central Wheat Belt districts are being told to take action to stay safe when the storms hit.

This includes staying away from trees, powerlines and drains, staying inside away from windows, unplugging electrical appliances and avoiding using landline phones.

A cold and unstable air mass has moved over the southwest of the state bringing brief but heavy storms.

The affected areas include Perth, Albany, Bunbury, Busselton, Dunsborough, Esperance, Katanning, Mandurah, Manjimup, Margaret River, Merredin, Moora, Mount Barker, Narrogin and Northam.

Heavy rain over the past week has already caused flooding in parts of the Avon River and Swan River catchments.

At Walyunga northeast of Perth, the Swan River is above the minor flood level at 3.87 metres and rising, with a peak above four metres likely overnight.

Residents are being advised to move equipment and livestock to safety and to pack an emergency kit.

Catchments saturated by recent storms combined with areas of flooding may adversely affect road conditions along the Swan River, authorities said.

Bridgetown and Nannup on the Blackwood River have seen minor flooding and there has been moderate flooding at Boyup Brook, after up to 25mm was recorded in the catchment up to Sunday morning.

At Bridgetown, the river has reached just over four metres and is still rising, with a peak predicted late Sunday.