Crops flattened, towns smashed by rampaging cyclone

Local farm and produce store Bumbak's was one of the properties impacted by the storm as it tore down the Western Australia coast.

"The corn has been absolutely flattened, the tomato seedlings have been wind blasted, they won't be able to produce anything," owner Jo Bumbak told AAP on Sunday.

Ms Bumbak said a nearby avocado farmer had been "entirely wiped out" with fruit strewn across the ground.

The Carnarvon region supplies about 60 per cent of the state's fresh produce during winter months, and 80 per cent of bananas.

Mature trees on banana plantations had been badly damaged, Ms Bumbak said, but younger plants had survived remarkably well.

Emergency services warned residents of the area that the Gascoyne River, which cuts through the state's inland to Carnarvon, was due to flood on Sunday afternoon and they might be cut off.

Recovery and clean-up work following the storm was likely to take weeks, Emergency Services Commissioner Darren Klemm told reporters.

After lashing coastal communities with 250km/h winds and dumping a year's worth of rain in a day, the now-subtropical low headed offshore overnight after weakening as it tracked inland east of Perth.

Exmouth, located on the North West Cape, bore the brunt of the category-four cyclone, which first crossed the Queensland coast more than a week earlier.

Four structures have been confirmed destroyed and 27 damaged though authorities expect those numbers to climb as more than 2000 homes in the area are assessed.

Power had been returned to 250 homes in the area on Sunday morning and emergency crews had arrived to help restore services to the remainder.

But provider Horizon Power warned some areas could be without electricity for long periods due to problems with access and safety concerns.

Work was also under way to repair water infrastructure.

Roads were being progressively cleared to allow emergency services and supplies through, although some remained inundated and too dangerous.

The town's airport has been extensively damaged and commercial flights are grounded.

Premier Roger Cook urged tourists to contact operators before changing any travel plans as the Easter break approached.

"We don't want them to not go and spend their dollars in those regional towns," he said.

State relief payments of up to $4000 have been made available to cover the immediate needs of residents, such as temporary accommodation or emergency transport.

Exmouth local Craig Kitson said the devastation in the town was extensive. 

"The town has fundamentally changed," he said.

Although he lost a fence and spent the night under a leaking roof, Mr Kitson counted himself lucky.

"Some people's lives have been drastically changed," he said, adding some homes had been completely destroyed.

Narelle tracked south to Coral Bay and crossed the coast on Friday evening just south of the tiny town before weakening to a category-three system.

It was downgraded again northeast of Kalbarri and Geraldton before weakening to a tropical low on Saturday morning.

Narelle has also exacerbated the global energy supply crunch by disrupting production at two of Australia's biggest liquefied natural gas plants, run by Chevron and Woodside.