Cyclone Veronica has weakened to a category one system off WA's Pilbara region and conditions have eased in Port Hedland after the coast was "pummelled" for 24 hours, but the threat of major flooding remains.

Key points: Authorities are warning the danger from Cyclone Veronica is not over yet

Authorities are warning the danger from Cyclone Veronica is not over yet A red alert remains in place west of Port Hedland to Mardie, including Karratha

A red alert remains in place west of Port Hedland to Mardie, including Karratha The cyclone has already dumped hundreds of millimetres of rain on the region

The eye of the cyclone is tracking westward parallel to the coast, causing heavy rainfall and flooding between Karratha and Port Hedland, despite having earlier been expected to reach land.

Destructive winds have brought down trees and damaged buildings, while flooding sparked by heavy rainfall has left a number of homes in Boodarie near South Hedland stranded on temporary islands.

A cyclone red alert has now been lifted in Port Hedland and South Hedland, with residents cleared to leave their homes.

But a red alert remains in place for communities west of Port Hedland to Mardie, including Karratha.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 6 seconds 1 m 6 s Damaging winds from Cyclone Veronica leave mark in Karratha

Department of Fire and Emergency Services (DFES) spokesman Darragh Wills said the danger was not yet over.

"It is still a cyclone, and there is still the red alert in force," he said.

"It is forecast to track west, so the impact will move along the coast along with that, although it is moving very slowly.

"If it moved more quickly the rain would go along with it, but it's in the one spot more or less and the rain just keeps falling, so you'll get all that rain in a smaller area."

Port Hedland locals assess damage

Mr Wills said DFES had received no reports of injuries, but there had been isolated power outages and minor damage.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 35 seconds 35 s Cyclone Veronica batters the Pilbara

The streets of Port Hedland were choked with vehicles once the red alert was lifted this morning, after the population of 14,000 had been in lockdown for 42 hours.

Those who had evacuated raced home to check for damage while some went straight to the few open shops, and others to simply to get some fresh air and look at the storm's aftermath.

All through Port and South Hedland there were downed trees and broken fences.

Much of Cemetery Beach Park in Port Hedland remains flooded following a storm surge. ( ABC News: James Carmody )

Rubbish and debris was scattered across the road and large rocks from the harbour had been lifted by the strong winds and scattered along the road near the port.

However, the SES said initial surveys showed there had been minimal serious damage.

Port Hedland resident Ayla Stewart said she and her son had endured a sleepless night as the winds intensified, and had been unable to leave their house this morning because of a large tree that had fallen across their driveway.

Ayla Stewart and her son wait for help after a tree blocked their driveway. ( ABC News: Kathryn Diss )

"It wasn't until the early hours of Saturday morning that the tree fell down and from then it's been a lot more chaos with the neighbour's tree falling down," she said.

"At the moment [we are] just waiting for the SES to come in and set us free — we're a little bit trapped."

DFES has deployed extra staff to the region, including a taskforce from its statewide operational response division and an urban search and rescue taskforce.

Horizon Power has been working with communities across the region to restore power outages.

In a statement it said the Town of Port Hedland received the all clear earlier on Monday, enabling power crews to start assessing damage to its electrical infrastructure and start restoration works where it was safe.

"Thanks to the efforts of our crews, we have successfully restored power supplies to a number of affected areas, including South Hedland and [the] majority of Point Samson earlier today," the statement said.

About 40 customers in the City of Karratha, 16 in Point Samson, 2 in Roebourne and 20 customers on the Dampier airport feeder were still without power.

Department of Communities staff have fed hundreds of people at the Karratha evacuation centre. ( Supplied: Natasha Bargeus-Claite )

Cyclone heads west amid flooding threat

The Bureau of Meteorology (BOM) said the cyclone was still packing winds of up to 85 kilometres per hour near its centre, with gusts of up to 120 kph.

It has begun to increase in speed as it moves west off the coast, but is set to weaken further this afternoon, and is likely to be downgraded to a low this evening.

Children made the most of the floodwaters in Port Hedland. ( ABC News: James Carmody )

However, the BOM has warned of widespread heavy rainfall conducive to major flooding over the Pilbara coast and adjacent inland areas.

BOM acting state manager James Ashley said flooding was now the main concern.

"Whilst the worst of the wind conditions are easing and have passed, heavy rainfall is still expected in that area between Port Hedland and Karratha and inland parts of the Pilbara," he said.

"So our focus has moved from the wind impacts of the cyclone to this heavy rainfall and the flooding effects that will cause.

"The peak recording we've had to the south of Port Hedland was 360 millimetres to 9am [Monday] morning.

BOM said flooding was now the main concern for authorities. ( ABC News: Marcus Alborn )

"For the remainder of today we're expecting another 100 to 200mm to fall through that area between Karratha and Port Hedland and particularly inland, through that south-eastern part of the Pilbara towards Marble Bar.

"So with those extra heavy falls on top of what's already fallen, flooding will be a problem."

'Stalled' cyclone battered coast for 24 hours

Mr Ashley said the remarkable feature of the cyclone was the length of time it stalled off the Pilbara coast.

Trees were uprooted in Karratha as Cyclone Veronica hit. ( Supplied: Dylan Hansen )

"It was really unusual in the fact that it moved really slowly southwards and then stalled just off the coast, pretty much halfway between Port Hedland and Karratha, and stayed there for about 24 hours and pummelled that coastline," he said.

"This system will probably lead to the longest period of gales that we've recorded at Karratha and Roebourne — periods in excess of 24 hours."

DFES Commissioner, Darren Klemm, reiterated the warning that people should steer clear of floodwaters.

"If it's flooded, forget it. We don't want to see people swimming in flood waters that can be of unknown depth and can be fast moving," he said.

Commissioner Klemm said DFES had received 54 requests for assistance, but the extent of the damage was not yet known because a red alert was still in place for some areas.

The clean-up is anticipated to take at least one week.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 11 seconds 11 s Cyclone Veronica rolls into Karratha

Nine arrested after reports of looting

Police have arrested nine people in relation to burglaries on Port Hedland businesses while the town was on curfew.

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Police believe several children under the aged of 10 were part of a group that allegedly broke into four businesses during lock down when the city was on red alert.

Two adults have also been arrested.

Schools in the region were closed today, including those in Port Hedland, South Hedland, Karratha, Marble Bar, Roebourne, Wickham and Dampier.

A number of roads were also closed, including a large stretch of the North West Coastal Highway.

Main Roads said in a statement there was no evidence of any major road damage at Port Hedland, but there had been heavy flooding across sections of North West Coastal and the Great Northern Highways and other major roads in the Pilbara.

Main Roads executive director Des Snook said it could be a few days before some of the more badly affected sections of highway could be reopened to traffic.

"The priority is to assess the safety and condition of the highways and main roads and re-open them soon as possible," Mr Snook said.

Economic blow could exceed $1 billion

Ports are also closed, including at Port Hedland, the biggest iron ore exporter in the world.

Destructive winds buffered Port Hedland as Cyclone Veronica bore down on the coast. ( Supplied: Joe Carbone )

Analyst Phillip Kirchlechner has warned the cyclone could cost the nation's economy more than $1 billion.

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"Based on iron ore exports out of Australia in recent years, which range from roughly $US60 billion to $US70 billion a year, if [shutdowns last] about a week and there's no catching up of lost production later, then the impact would be around $US1-1.3 billion," he said.

Mr Kirchlechner said that cost could be greater if the cyclone caused damage to mining infrastructure, further delaying a resumption of exports.

The Pilbara Ports Authority is uncertain when it will reopen its facilities, which have now been closed for three days.

BHP said in a statement initial inspections had shown water damage to some buildings at its Nelson Point rail and port facilities in Port Hedland.

It said it was "currently working through the situation" which could impact on employees returning to work.

Sutherland Street at Cemetery Beach in Port Hedland was temporarily inundated during the cyclone. ( ABC News: James Carmody )

Babies born in cyclone

At least five babies have been born in affected communities during the cyclone, including baby Wynter, who was delivered at Karratha Health Campus early on Sunday.

Parents Danielle Boyle and Ryley Drummond thanked hospital staff for their efforts during the cyclone.

Baby Wynter was born as Cyclone Veronica lashed the Pilbara coast. ( Supplied: Family )

"Although the winds and rains were picking up outside, things couldn't have been calmer or more relaxing in the hospital," they said.

"Wynter made her arrival into a peaceful atmosphere thanks to the wonderful staff and support at Karratha Health Campus.

"We can't thank you enough."