Hundreds of properties in the West Australian town of Kalbarri are feared to have been destroyed or sustained major damage from Tropical Cyclone Seroja.
No deaths or major injuries have been recorded.
Much of the carnage was concentrated in popular tourist spot Kalbarri, 580km north of Perth and home to about 1,400 people.
Premier Mark McGowan on Monday said up to 70 per cent of properties in Kalbarri had some damage.
About 40 per cent of those properties are believed to have sustained major damage including total loss.
"This is heartbreaking," Mr McGowan told reporters.
"All West Australians are thinking of those people who have been affected. The next few days will be very tough and difficult but we will get through this together."
Cleanup has now begun.
Seroja made landfall south of Kalbarri about 8pm on Sunday as a category three storm with wind gusts up to 170km/h.
It has now been downgraded to a tropical low and moved offshore near Esperance on WA's south coast.
A red alert has been lifted for Kalbarri but remains in place in nearby Northampton, where residents are urged to stay home.
Mr McGowan, who is expected to visit Kalbarri on Tuesday, said it was too early to quantify the total damage but many areas had been affected.
More than 31,500 homes remained without power in Kalbarri, Geraldton, Northampton, Dongara, Port Denison and Mullewa as of Monday afternoon.
"Power returning may be a matter of days, not hours, given the significant damage to infrastructure across a very wide area," the premier said.
Sewerage and telephone infrastructure in Kalbarri has also been damaged.
Evacuation centres have opened in Shark Bay and Dongara and a third centre will open in Geraldton later on Monday.
Food, clothing and personal items are being provided.
State Emergency Service personnel are set to be assisted by volunteers flying in from other states.
Mr McGowan said he had been in touch with Prime Minister Scott Morrison and a disaster relief fund would be activated.
The Australian Defence Force will provide a C-130J Hercules aircraft for medical evacuations and to transport emergency workers and supplies.
"Defence is also considering a request from WA for boots on the ground to assist with clean up and damage assessment," Federal Emergency Management Minister David Littleproud said.
"These communities need assistance now and we are acting immediately."
Reports of property damage and power outages in Kalbarri and Geraldton began to emerge as the storm's force was felt and residents took shelter by candlelight.
Fallen trees, damaged homes and wrecked fences could be spotted amid the howling wind and rain in social media footage.
Wind gusts recorded around Kalbarri were likely to have been the strongest in more than 50 years, the Bureau of Meteorology said.
"I've never experienced anything in my life like we experienced last night," resident and caravan park manager Debbie Major told ABC TV.
"It's only a small town ... half of it has been flattened."
The combined state and federal disaster relief is expected to exceed the $18 million spent on the Woorooloo bushfires which destroyed 86 homes northeast of Perth in February.
