A powerful, slow-moving cyclone is bearing down on the West Australian coast, bringing destructive wind gusts, flooding rain and dangerous tide surges over a prolonged period.

Cyclone Veronica was downgraded to a category three system as it began lashing the coastline of the Pilbara region between Dampier and Port Hedland about 6am on Sunday.

The tide beginning to rise in Port Hedland on Friday. Credit:Facebook / David Petersen

The Bureau of Meteorology says a severe coastal impact is expected as early as mid-morning, but more likely during the afternoon.

Authorities in the Pilbara have issued a red alert, telling residents between Pardoo and Mardie to take shelter immediately and brace for howling winds and rising tides.