Evacuations ahead of Yasi

This morning, Yasi was still well out to sea but had intensified to a severe category three system.

It's expected to cross the coast as a severe category four, with winds gusting up to 250km/h, very late tomorrow night into Thursday morning.

The most likely landfall position is somewhere between Cooktown and Townsville, the Bureau of Meteorology says.

Yasi is expected to deliver a very large storm surge, and the bureau is working to provide emergency services with the latest advice so they can better focus evacuation efforts.

But some communities are not waiting.

Island resorts in the Whitsundays are being evacuated along with low-lying parts of other communities in the danger zone, initially said to reach as far south as Proserpine, near Mackay.

Queensland Premier Anna Bligh has warned the cyclone could be the worst the state's ever seen, with the potential to cause "powerful and deadly" flash flooding, especially in low-lying areas near the coast.

Whitsundays Mayor Mike Brunker said there was a sense of urgency in the community.

"People in low-lying areas are evacuating to friends and family or, if they have to, leave town," Mr Brunker said.

"They should be very anxious as there's no time for complacency."

He said residents had been panic buying food and supplies since Cyclone Anthony, which crossed the coast near Bowen late on Sunday night as a category two storm. It caused little damage.

Forecasters have said Yasi will be similar in strength to Cyclone Larry, which devastated Innisfail and surrounds in 2006.

But its physical size is much greater, meaning it will affect a much larger part of the coastline.

And with strong monsoonal activity feeding the storm, it's expected to remain a cyclone long after it makes landfall and could even reach as far inland as Mt Isa as a cyclone with destructive winds, the bureau has warned.

Ms Bligh said Yasi was a very serious threat, both in terms of its winds and its capacity to deliver more floods to an already waterlogged state.

"We could see very powerful flash flooding that will be dangerous and potentially deadly," she said.

"We're not only confronting a very dangerous cyclonic event, we are confronting the very real possibility of significant further river flooding."

The central Queensland centres of Rockhampton and Emerald, recovering from near record floods in January, are facing further inundation in the days after the cyclone.

Ports from Cairns to Mackay will close today, along with some schools.

Townsville Mayor Les Tyrell said residents in low-lying areas vulnerable to tidal surges were being urged to leave their homes today.

He said 200 nursing home residents were also going to be evacuated and schools would most likely be closed tomorrow.

"People need to be aware the system is a large one and people living in an area at risk of a tidal surge should leave today," Mr Tyrell said.

"Also, people need to find the safest place in their home, it's generally the bathroom, but a room without windows is ideal (as a cyclone bunker)."

Cairns residents in low-lying areas are being told to leave their homes.

Mayor Val Schier said nursing homes have evacuation plans in place but so far they have not been activated.

"We're telling anyone in the low-lying areas they need to be moving today and find another place to go to," Ms Schier said. "We're expecting the first gales and winds will be tomorrow morning.

"It is intensifying and it is looking at this point to be bigger than Cyclone Larry."