A severe thunderstorm warning is current for areas between Lancelin to Gingin to Manjimup to Busselton, including people in, near or between Perth, Mandurah, Bunbury, Busselton, and Bridgetown.
These areas are likely to be hit by damaging winds and heavy rain.
The Weather Bureau says there are thunderstorms with very heavy rainfall in a line from just north of Bunbury to Wandering.
The front is moving slowly south.
There are more storms south of this area and they could extend to remaining parts of the warning area during today, the bureau said.
Very heavy rainfall which may lead to flash flooding with one-in-50-year rainfall intensities has been observed in the areas between Mandurah and Harvey.
Storms may be accompanied by damaging winds and heavy rainfall which may cause flash flooding.
Bureau of Meteorology duty forecaster Matt Boterhoven said while some areas experienced slowly accumulated rainfall over the past 12 hours, Mandurah had 30mm of rain in an hour.
Harvey recorded 80.2mm of rain, with 46.2mm falling between 5am and 6am, Myalup received 66.6mm, Serpentine recorded 42.88.mm and 38.6mm fell at Garden Island.
Mr Boterhoven said heavy rainfall and thunderstorms where expected to continue until Friday.
“The mid-level disturbance is going to linger near the west coast today and then eventually later tomorrow it will start moving eastwards and away from the lower-west and south-west districts,” he said.
The Department of Fire and Emergency Services answered more than 100 calls for help overnight, 86 of which were from Rockingham.
Most of the reported damage involved flooding and roof damage.
State Emergency Service volunteers are responding to damage on a priority basis and have asked people to remain patient.
There are currently more than 70 volunteers from nine units working in the Rockingham area and a further six units are being deployed.
They are making temporary repairs to homes, fixing minor roof damage, removing fallen trees, sandbagging areas in danger of flooding and pumping out flood water.
Residents in affected areas are being told to stay away from fallen powerlines, be careful of fallen trees, debris and damaged buildings and check on friends and neighbours.
There is a strong wind warning out today for Perth Local Waters, Ningaloo Coast, Gascoyne Coast, Geraldton Coast, Lancelin Coast, Perth Coast, Bunbury Geographe Coast, Leeuwin Coast, Albany Coast and the Esperance Coast.
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