A severe tropical cyclone smashed into Western Australia's north coast on Saturday, forcing residents to bunker down as they waited for the destructive gale-force winds to pass.

Cyclone Lua, upgraded to a Category 4 storm -- five is the highest -- hit the sparsely populated Pilbara region and was moving inland, with winds estimated at 250 kilometres (155 miles) at its centre near the shore.

"It's a fairly black sky and the winds are picking up quite strong and we're getting lots and lots of rain and the ocean is absolutely boiling," ranger Pete Morris told the ABC ahead of the cyclone making landfall.

"So we're sort of just bunking down."

The small communities of Pardoo and Wallal were expected to be worst hit, with the Bureau of Meteorology warning winds of up to 160 kilometres per hour from Port Hedland to Bidyadanga, near the resort town of Broome.

"Very Destructive winds to 250 kilometres per hour are forecast near the cyclone centre near the coast with gusts to 180 kilometres per hour possible over the inland eastern Pilbara," it said.

Western Australia's Pilbara region is an important resources hub, with major iron ore and gas facilities.

Commercial flights into the area have been cancelled and the main highway closed, while the Port Hedland port had been shut down.

Bureau forecaster Neil Bennett said the storm was powerful.

"Looking at the whole of Australia, this is the strongest cyclone of the season so far and the strongest one since Cyclone Yasi crossed the Queensland coast last year," he told the ABC.

Cyclone Yasi was the biggest storm to hit Australia in a century and wrought huge damage to small coastal communities in the eastern state of Queensland but did not cause any deaths.

Australia has been hit by extreme rainfall in recent weeks, with the eastern state of New South Wales, Queensland and Victoria all suffering floods after torrential downpours swamped scores of homes.

More residents were told to evacuate in New South Wales on Saturday amid fears that Murrumbidgee River, swollen by weeks of incessant rain and the floodwaters from upstream, would breach levees.

State Emergency Services have warned that the levees may not be able to hold back the waters from the town of Hay, with more than 500 properties in danger of inundation.