Cyclone Veronica weakened from a category 4 storm before its core winds hit the coast near the mining center of Port Hedland, but officials warned the system was slow moving and would continue pounding the region with gale force winds and heavy rain for 24 to 48 hours.
The Bureau of Meteorology said Veronicas forward movement had stalled around midday Sunday before its eye made landfall, and was forecast to weaken to a category 1 storm overnight and then veer west along the coastline.
It said the "severe" storm was producing wind gusts of up to 200 kilometers per hour (120 mph), pushing a storm surge of up to two meters (seven feet) onto the coast.
Rainfall was expected to hit 20-40 centimeters, it said."Tides are likely to rise significantly above the normal high tide mark with damaging waves and very dangerous coastal inundation," the bureau said.
Australias western coast usually sees three or four cyclones per year and emergency services said residents were well prepared for this storm.