The weather bureau has issued fresh warnings for Tropical Cyclone Fina, as it intensified on Monday and moved towards the northern coast of Western Australia.

Across much of the Top End, where Fina hit at the weekend, the clean has begun.

But many schools remained closed and thousands were still without power on Monday, though it appeared the Top End had been spared serious injuries and significant damage.

Darwin airport has had 157 millimetres of rain since 9am on Saturday, while Middle Point, south-west of the city, copped 393 millimetres.

Some Northern Territory homes faces days without electricity, with the Tiwi Islands north of Darwin among the hardest hit after the system swept through on the weekend.

“We’ve had destructive winds, mass power outages and there’s a big, big clean-up job to come,” NT Chief Minister Lia Finocchiaro said.

Authorities toiled through Sunday night and restored electricity to 5000 homes and businesses, but about 14,000 were still without power on Monday morning.

“When you look at the outage map, it is widespread,” Finocchiaro said.

“There are people who will be waking up this morning coming out of their second night with no power, and that has a huge impact.”

The Tiwi Islands were hit hard, with infrastructure badly damaged at the township of Wurrumiyanga on Bathurst Island.

Now that winds have calmed, energy crews are expected to be sent but the island community may be without power for days.

Authorities said there had been no reports of serious injuries on the islands.

Cyclone Fina was offshore on Monday, with a warning declared for a part of the sparsely populated north-east Kimberley coast.

The system is showing sustained winds of 185km/hr, with gusts near the centre reaching 260km/hr.

A “shelter indoors now” warning was issued for WA’s Cambridge Gulf to north of Faraway Bay.

“There is a threat to lives and homes. You are in danger and need to act immediately,” it said.

The cyclone passed between the Tiwi Islands and Darwin at the weekend as a category three system, with top gusts of 195km/h and sustained winds near its centre of 140km/h.

In Darwin gusts reached 107km/h, felling many large trees.

Of the NT’s 153 government schools, 66 were affected, with 15 closed on Monday.

Tiwi College will be close until further notice after extensive damage to school grounds and accommodation, along with flooding in the administration building.

“We have issues with water supply and there is much cleaning up around the grounds to make it safe for students,” the secondary school said on its Facebook page.

Federal Emergency Management Minister Kristy McBain said the Commonwealth stood ready to support the NT government.

Defence force personnel are already on the ground assisting in remote communities.

Fina was expected to gradually weaken by Monday afternoon, before it crossed the northern Kimberley coast later in day, the Bureau of Meteorology’s Jonathon How said.

The cyclone warning has been lifted in the NT.

-AAP