The category two cyclone Veronica is carrying destructive gusts of 155 kilometres per hour as it slowly tracks along the coast between Karratha and Port Hedland.

Premier Mark McGowan has urged people to stay indoors, even those who've experienced cyclones before.

"People in that part of the world are used to cyclones but this one is different," he said on Sunday.

Veronica weakened overnight on Sunday to a category two, from a category three, and will continue to head west on Monday.

"The system is forecast to weaken below tropical cyclone intensity during Monday evening," the bureau said.

But the danger will remain for most of the day with widespread and heavy rainfall likely to mean there will be major flooding over the Pilbara coast and adjacent inland areas.

"Heavy rainfall is expected to result in significant river rises, areas of flooding and hazardous road conditions," the bureau said.

A dangerous storm tide was also predicted to hit the region in the early hours of Monday morning and damaging waves are predicted to bring inundation.

Many communities remain at red alert status.

Australian Associated Press