UPDATE, 9.35pm: A wave height of 9.5m has been recorded off Townsville - 2.5m higher than when it was measured this afternoon, Premier Anna Bligh has announced.
Significant flooding is expected in some low-lying areas.
The number of power users now with blackouts has increased from 37,000 when announced at Ms Bligh's 8.30pm media conference to 61,000 customers.
She said the rate of power failure was accelerating considerably.
Calls to emergency workers were starting to increase, but only about 150 had been received from across the region.
More were expected from the Innisfail/Cardwell area soon.
Police also announced they had received their first distress call from a person in Port Hinchinbrook who needed to evacuate, but police had advised the caller to bunker down because it was too dangerous to relocate.
Earlier it was reported that the danger to police and emergency services meant they were already locked down like everyone else.
9.10pm: PREMIER Anna Bligh has warned Queenslanders they will wake up to shocking scenes from North Queensland tomorrow morning.
In a press conference she said Queensland could expect "scenes of devastation on an unprecedented scale".
"We will all have to brace for this," she warned.
"It will take all of our strength to overcome it."
"This cyclone is like nothing we have dealt with before as a nation."
Ms Bligh said the very early signs of Yasi were now starting to be felt, as power lines came down and outages occurred.
While the eye is now expected to cross the coast around midnight, the destructive core, about 150km wide, will cross up to three hours earlier.
"It is five times wider than the same core in Cyclone larry," Ms Bligh said.
The most damaging timeframe was expected to be between 8.30pm and midnight.
The North Queensland coast was also experiencing "very, very high storm surge activity", she said.
Point Cleveland had recorded a 6.6m wave height.
"This is the highest that has ever been recorded since measurements began in 1975", she said.
A high tide was expected about half an hour after the premier spoke.
"We will also see a high tide in this region around 9.30am tomorrow," she said.
The residual effects of high-powered winds could also cause a second peak of storm surging during and after the morning high tide.
The premier urged people not to go outside prematurely to assess the damage, and warned that live power lines may be down.
"You may be putting yourself in danger," she said.
"People need to be very mindful not to start moving about town too early."
Ms Bligh said downed power lines had already left 37,000 people were already without electricity in the Cardwell/Innisfail area.