The Bureau of Meteorology says Cyclone Ita, the category-five system bearing down on the far north Queensland coast, is showing no signs of weakening.

The weather bureau says Ita has slowed down as it heads towards the coast and is expected to make landfall between Cape Flattery and Cooktown around midnight.

The bureau says the cyclone has very destructive winds of up to 300 kilometres per hour near the core.

Authorities have locked down the main cyclone shelter in Cooktown as winds from Cyclone Ita become more dangerous.

Metal grates are across the main entrances at the PCYC Events Centre, with around 300 people shut inside until the storm threat passes.

Cook Shire Mayor Peter Scott says everyone should now be taking shelter in a safe place.

He says there are also smaller shelters in use in surrounding areas.

"I think we've got the vast majority here - talking about 300 people all up - that's I think 280 plus 20 services staff as well," he said.

"Hope Vale they've got nearly 700 out there - that's a large part of their population so good on them."

Cooktown resident Ivan Juff says locals are nervous but he has decided to stay put.

"I've seen what Cyclone Larry and all those did, and this is up there with them ... (but) I live here. I'm not going anywhere else," he said.

"All the council blokes, they've all got families and houses and that too and they'd be in the same boat as me.

"They're worried about the whole show. We'll get through it."

The weather bureau says the cyclone is the most severe system it has seen approach the Queensland coast since Cyclone Yasi in 2011.

It warns that the Cassowary Coast could receive up to 300 millimetres of rain every six hours for several days after Ita hits.

At noon (AEST) the system, which has already wreaked havoc in the Solomon Islands, was estimated to be 175 kilometres north-north-east of Cooktown and 330 kilometres north of Cairns, and moving south-west at 10kph.

A cyclone warning is current for coastal areas from Cape Sidmouth to Innisfail, including Cooktown, Port Douglas and Cairns, and extending inland to areas including Kalinga, Palmerville, Mareeba and Chillagoe.

Graham Elmes, who owns a cattle station in the Lakeland District west of Cooktown, says many families have evacuated their homes, but two workers will remain at the Butchers Hill property.

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"They're going to hunker down in the toilet systems there under the hall because it's sort of built in underground and that hall is made from a steel structure that we brought over from Archer's Point."

Hope Vale Shire banana farmer Kenny Reid is among those bracing for massive crop losses.

"It's always in the laps of the gods I guess, but we will do what all farmers do - head down, bum up after the event and we'll do what we need to do to bring it back to its feet," he said.

Structures could be vulnerable

Tropical cyclone category system Category five Extremely dangerous with widespread destruction

Extremely dangerous with widespread destruction Very destructive winds - typical gusts over flat land of more than 280kph Category four Significant building damage likely, many caravans will be blown away or destroyed

Significant building damage likely, many caravans will be blown away or destroyed Dangerous airborne debris and widespread power failures

Dangerous airborne debris and widespread power failures Very destructive winds - typical gusts over flat land of 225-279kph Category three Some damage to roofs and buildings, some caravans will be destroyed

Some damage to roofs and buildings, some caravans will be destroyed Power failures likely

Power failures likely Very destructive winds - typical gusts over flat land of 165-224kph Category two Minor house damage, significant damage to signs, trees and caravans

Minor house damage, significant damage to signs, trees and caravans Heavy damage to some crops, risk of power failure, small craft may break moorings

Heavy damage to some crops, risk of power failure, small craft may break moorings Destructive winds - typical gusts over flat land of 125-164kph Category one Damage to some crops, trees and caravans; crafts may drag moorings

Damage to some crops, trees and caravans; crafts may drag moorings Gales - typical gusts over flat land of 90-125kph Source: Bureau of Meteorology

Councils in the region say they are prepared for electricity supply to be cut to some communities for up to a month.

Swift water rescue crews and SES volunteers are on standby in Cooktown and Cairns.

Cooktown residents are being warned that properties built before 1985 may not be able to withstand Ita's impact.

It is believed one third of dwellings in the town of about 2,400 people could be vulnerable and Premier Campbell Newman has urged people in those houses to seek shelter elsewhere.

Sue Brennan is one resident who has decided to remain at home.

"We're building a house, so we've locked down that house and tied the trailers to trees and stuff like that with chains," she said.

"We're forgetting about up the top and just going downstairs underneath in a smaller room with the shower and toilet and food."

Mr Newman has warned that Ita has the potential to cause large storm surges similar to those created by Typhoon Haiyan in the Philippines last November.

He says a category-five cyclone is as bad as it gets.

"Frankly I don't know if we all understand enough about the impacts of storm surge," he said.

"Think about some of the photos we saw or the footage we saw of the Philippines last year - that's the sort of thing that can happen. Beachside properties are the ones that it impacted.

"Now I stress that at this stage that's not the problem, but if the track changes and moves further south then that is the sort of impact you can have."

The weather bureau says the sea is "likely to rise steadily up to a level which will be significantly above the normal tide, with damaging waves, strong currents and flooding of low-lying areas extending some way inland".

"People living in areas likely to be affected by this flooding should take measures to protect their property as much as possible and be prepared to follow instructions regarding evacuation of the area if advised to do so by the authorities," it said.