Debbie wreaked destruction throughout north Queensland as a category 4 on Tuesday before weakening and moving south, bringing pelting rain, strong winds and flash-flooding to the state's south-east.

Hundreds of streets were closed in flash floods throughout Brisbane, the Sunshine Coast, Ipswich and the Gold Coast, with sandbags used to protect properties.

By 8pm, almost 93,000 homes and businesses across south-east Queensland were without power. An Energex spokesman said the flooding and debris would hamper the efforts of the 40 Energex crews working overnight to restore services.

A flood watch was in place for coastal catchments between Hervey Bay and the NSW border, extending to the Maranoa and Warrego, Darling Downs and Granite Belt districts.

State, independent and Catholic schools and childcare centres were closed from Agnes Water to the NSW border, and will be closed again on Friday.

Almost 90 year 7 students from St Augustine's College in Springfield, Queensland, were trapped at a school camp in northern NSW.

A Brisbane Catholic Education spokesman said the Uki campground, which the children were due to leave on Friday, was cut off by floodwaters, but they were safe, being looked after by seven teachers.

Residents in northern New South Wales were also ordered to evacuate ahead of major flooding, with the SES telling people in the areas of South Murwillumbah, Condong and Tumbulgum to leave if safe to do so.

Major flooding was forecast along the Tweed River with levels predicted to be similar to 2001 and 2008 floods, after almost 400 millimetres of rain fell in 24 hours over the Tweed River valley.

The extreme weather forced authorities to suspend a search for a bushwalker missing in Lamington National Park, on the Queensland-NSW border.

More than 380mm of rain was recorded at Springbrook in the Gold Coast hinterland in the 12 hours to noon, with some areas expected to be pounded with more than 500mm of rain into the night.

There were 51 swiftwater rescues in south-east Queensland, more than 1000 calls to the SES by Thursday afternoon, with more expected, and more than 11,000 properties without power.

A family trapped in a home at Sarabah on the Gold Coast hinterland made it to safety, despite emergency crews unable to access their property due to raging waters. The family of one man and four children was able to evacuate at the back of their property.

On the Sunshine Coast, a swiftwater rescue team waded through metre-high fast-flowing water for 20 minutes to rescue a family at Tanawha.

An emergency alert was also issued for residents in the Tallebudgera Valley area, who were warned to prepare for short-term isolation as water levels rose.

Beaches along 600km of coastline, Gold Coast theme parks, university campuses, the Queensland Museum, Gallery of Modern Art and many shops were closed, flights were delayed or cancelled into Brisbane Airport and all criminal matters at Brisbane's Supreme and District courts were adjourned.

Public transport suffered delays but was free on the TransLink network from 10am to get people to safety and non-essential public servants in the south-east were told to go home.

Non-essential services and appointments at some hospitals across south-east Queensland and Mackay were postponed but emergency departments continued to operate.

Premier Annastacia Palaszczuk urged people to stay at home, indoors and off the roads on Thursday night, to allow the roads to remain clear for emergency services.

Thousands of workers heeded the message, with the usually bustling Brisbane CBD almost deserted by Thursday afternoon.

Winds were expected to double in intensity in the south-east to about 60-70km/h, but would be stronger in coastal areas.

Bureau of Meteorology meteorologist Matthew Bass predicted wind gusts of more than 125km/h in coastal areas, including the Wide Bay, with heavy rain and flash flooding predicted on Thursday night.

Rain was predicted to clear by Friday morning, although dangerous surf conditions were likely on Friday and Saturday.

Queensland Fire and Emergency Services Commissioner Katarina Carroll said it was "extraordinary" there had not been more injuries and urged people to stay safe after seeing someone riding a jetski in a flooded Gold Coast park.

The Gold and Sunshine coasts and Ipswich opened evacuation centres for people affected by the storm.

Insurers hit with at least 2500 claims for damages were bracing for more.

In the state's north, authorities discovered 10 electricity towers "folded like cardboard" in the aftermath of the cyclone.

Energy Minister Mark Bailey said the felled transmission towers would not affect energy supply but would weaken the system and supply could be routed by other means.

RACQ helicopters rescued people across the central coast as floodwaters left many stranded, and there were dozens of rescues in Mackay, with people on rooftops and in cars.

RACQ CQ Rescue crewman Arno Schoonwinkel said cane crops in the region were absolutely "annihilated" by floodwaters and the countryside was littered with debris, including people's personal belongings.

"There's a huge amount of water lying about and cane paddocks are all completely washed out. There's debris everywhere like chairs and tables from inside people's houses just floating in the middle of paddocks," he said.

Holidaymakers and staff started to be evacuated from Hamilton Island, with the airstrip opening, although long queues were expected, and the defence force flew in food, water and fuel to Daydream Island.

Daydream Island evacuated all guests and 116 staff by Thursday afternoon, with assessments of the extent of the damage carried out, and no new arrivals accepted until at least April 30.

Hayman Island received clearance for a boat to leave the resort for Hamilton Island and chartered a private plane to transfer guests to Sydney.

Ms Palaszczuk reassured north Queenslanders who bore the brunt of Cyclone Debbie that "we are with you".

"I travelled to your region yesterday and I saw first-hand the damage that she has inflicted on our beautiful towns that have now been devastated," she said.

Ms Palaszczuk said severe weather conditions were still hampering efforts to provide relief in the north.

The normally vibrant tourist town of Airlie Beach was a "ghost town" on Thursday.

Luke Harley said his Mantra Club Croc hotel lost power on Monday night and water on Wednesday.

"[Guests] are filling up toilet cisterns with buckets of water from the pool, we're rationing bottled water for them."

Mr Harley said the town was "apocalyptic", roads were cut off and phone reception was down, except for Telstra.

"All the trees have got all the bark stripped and the leaves off them," he said.

"There's a lot of damage to roads and flooding. Everyone's in good spirits and that's all we can ask for."

- Felicity Caldwell, Amy Mitchell-Whittington, Jorge Branco, wires