Australia's north is bracing for coastal crossings of two dangerous cyclones in coming days, as the Northern Territory conducts its biggest pre-storm evacuation and the Pilbara's iron-ore ports prepare for a hammering.

Tropical Cyclone Trevor, which crossed the Cape York peninsula this week, is expected to re-intensify into a category-four strength tempest by Friday afternoon with "very destructive winds" reaching gusts of 275 km/h. It is forecast to cross the Northern Territory's Gulf coastline near Borroloola on Saturday afternoon.

Twin tropical cyclones, Veronica in the west and Trevor in the east, will pose risks for wind damage, flooding and storm surges in coming days. Credit:Himawari-8

Off Western Australia, Cyclone Veronica has already reached category-4 strength with wind gusts of 260 km/h, the Bureau of Meteorology said.

The storm is expected strengthen to a category-5 event by later on Thursday as it pivots towards the coast between Karratha and Port Hedland, with gusts nearing 320 km/h. A crossing is expected on Sunday.