Queensland Premier Anna Bligh has warned residents that there could be devastation and heartbreak on an unprecedented scale as Cyclone Yasi smashes into the state.

North Queensland residents are feeling the full force of one of Australia's worst cyclones, with the category-five storm crossing the coast near Mission Beach, south of Innisfail.

Yasi, packing winds up to 290 kilometres per hour, slowed as it approached the coast and was moving west south-west at 25kph.

Hundreds of thousands of people are sheltering in evacuation centres and homes across the region as strong winds and heavy rain lash hundreds of kilometres of coastline.

In Cairns, trees are thrashing violently and some are bending over, while street signs are rattling.

Power has been cut to the main evacuation centre in Cairns at Earlville shopping centre, where about 2,000 people are taking refuge.

A total of 152,000 customers are without power across the region, including the Townsville CBD where a number of evacuation centres are located.

Townsville resident Robert White lives in a four-storey waterfront unit and says he is struggling to stop his glass doors from shattering in the raging wind.

"The waves have been unbelievable, and the wind... I can't believe it," he said.

"We've got a glass frontage on our unit and we've put our lounge suite and everything against the windows and the doors because they're all glass and we're just trying to hold them together at the moment."

Ms Bligh says the potentially deadly system is the "most catastrophic storm ever seen" in the state, and as well as destructive wind gusts it could also cause a tidal surge as high as nine metres.

The Premier says she cannot sugar-coat the situation and that it will be a tough night and a tough few days for people in north Queensland.

"We are in completely uncharted waters," she said.

Innisfail resident Craig says the weather is wild.

"This is the scariest thing ever. I think my roof's about to go, but I'm not 100 per cent sure."

Ms Bligh says a storm surge of about seven metres above the high tide mark is expected to hit some areas, including the town of Cardwell, which now resembles a ghost town.

"Cardwell's a small town of about 3,000 people and they've all been evacuated today, but you can begin to think of the catastrophic damage that we might find tomorrow morning," she said.

Ms Bligh has also warned there could be a catastrophic failure of power services in the days after Yasi, and given its size it could have a two to three-day life span.

The Premier says there is very little power generation capacity in the cyclone-affected area and that a spine of transmission towers carries electricity from central Queensland to Cairns on an inland route west of Townsville, while another spine of towers carries the electricity to south of Mackay.

She says these transmission towers are likely to be severely damaged, and if that happens the region could be without power for a long period.

"It will not only take all the strength of those people who are enduring it, [but] we as a community and Australians need to prepare for what we are likely to wake up to tomorrow," she said.

"We will all have to brace for this. It will take all of us and all of our strength to overcome it."

Flood threat

Wind gusts of more than 110kph are battering Townsville, but across the city it is the flood threat more than the wind that is making people anxious.

"The thing I'm most worried about is tidal movements," one resident said.

Mr White says he saw a yacht float away and sink.

"It is absolutely blowing a gale and I mean it's really strong - the rain is unbelievable," he said.

"We've still got a long way to go I reckon, so I think we're going to get a fair bit more, a fair bit more yet."

Glenda from Ravenshoe, west of Innisfail, says she is on an isolated property and is worried about her horses.

"We couldn't get any tape for our windows so we tried to use wide sticky tape but it's peeling off ... we are very scared. One side of our whole house is just glass," she said.

"We are actually camping under a desk that is bolted to concrete walls on two sides."

Wind speeds have also increased around the Mackay and Whitsunday region to the south.

Residents have been told to stay inside until the massive cyclone, which is five times wider than Larry, passes.

Authorities are warning that emergency services will not be able to attend calls for help during the height of the cyclone, but they are already planning the emergency response for when it is safe to leave shelter.

Yasi is expected to reach Mount Isa, around 900 kilometres from the coast, as a category-one cyclone on Friday.