The town of Carnarvon is on track to break its annual rainfall average in less than two days.
It has already broken records for the wettest day and the wettest month.
The Bureau of Meteorology says the sudden deluge has been caused by a monsoonal low.
The Bureau’s Neil Bennett says more than 210 millimetres of rain has fallen since yesterday morning.
“If we continue to see rain falling there is every chance that we could have seen the annual average rainfall of 225mm falling at Carnarvon in a period of around 36 hours, so this has just been an incredible event,” he said.
The State Emergency Services says it has received numerous calls from Carnarvon residents whose homes and businesses have flooded.
The SES’s Ray Edwards says workers are doing their best to attend to all calls.
“What we would like residents to do is, if there’s water coming through their roof definitely switch all power off at the box, and make sure no one turns it back on,” he said.
“Electrocution is a great risk, we also ask that they get out there and they look around their house and they dig drains and try and keep the water flowing away from their houses.”
SES workers have been sandbagging doorways, clearing collapsed ceiling debris and pumping out floodwaters.
Just north of Carnarvon, at Quobba station, Tim Meecham says the deluge has been phenomenal.
“I’ve been here for 32 years. It’s the first time ever that the whole of the shearing shed yards and the floor of the shearing shed is under water,” he said.
“Considering it’s all sitting on a sand hill, 50 metres from the beach it’s had a good drink and it’s fairly well saturated the ground.”
The Wooramel roadhouses’ Sharon Young says it has been pouring down.
“As far as I can see, all I can see is a big lake of water,” she said.
The North West coastal highway remains closed from north of the Shark Bay turn off through to Carnarvon and from Carnarvon through to the Minilya Roadhouse.
Other roads in the Gascoyne are currently open but there is a warning there could be flash flooding.
Motorists are being advised to slow down and turn lights on if driving through heavy rain, or if necessary, to pull over and park.
Authorities have issued a flood alert for Exmouth, Coral Bay, Carnarvon, Denham, Kalbarri, Meekatharra, Laverton and Paynes Find.
People living between Exmouth and Kalbarri are being told to prepare for heavy rainfall, coastal streams rising and flash flooding.