Flooding has begun and Queensland residents are scrambling for sandbags as they prepare for the deluge no one saw coming.
The extreme weather event is the unexpected sting in ex-tropical Cyclone Debbie's tail, and is expected to bring with it half a metre of rain.
Southeast Queensland is shutting down with rain becoming so severe Queensland authorities have made the unprecedented call to close all schools in the state's southeast and everyone from Mackay to Brisbane and the Gold Coast has been told to go home.
That's the startling advice from Queensland Police Commissioner Ian Stewart as the remnants of catastrophic Cyclone Debbie move south, bringing heavy rainfall as far as Sydney today.
"The clear message from us today is do not underestimate the power and potential of this rainfall. This can't be underestimated all down the eastern seaboard," Mr Stewart said.
"We need to make sure we are taking action, strong action, now."
Queenslanders are being advised to stay home or leave work early and collect their children ahead of forecast falls of up to 500mm in some parts.
Though the extreme weather event's peak is not due until early afternoon, Brisbane has already recorded a month's worth of rain in 24 hours and residents have begun sandbagging their properties. Flooding has already begun in areas across parts of Brisbane and the Gold Coast.
"If I was an employer I'd certainly be thinking about closing down by lunchtime," he said.
"People will be thinking about their kids, families, you don't want to them stuck at home, you don't want them worrying.
"If someone calls out for help we need to get there fast. We don't need our roads clogged up with people who are acting too late."
Locals were warned peak hour would be "a nightmare".
"The other message for today is that peak hour will probably be a nightmare this afternoon, so if employees can be staggered in terms of being released from work to go home, that would be the best thing possible in terms of ensuring that our road network is not clogged up," Deputy Premier Jackie Trad warned.
Some people are already ignoring warnings from authorities. Footage send to Channel 9 shows Gold Coasters riding jet skis around a flooded dog park.
Queensland's Minister for police fire and emergency Mark Ryan said warned road visibility would be low and driving conditions would be challenging.
"If you can avoid travelling on the road please do," he said. "We don't want to lose a Queenslander in this event."
Residents all across southeast Queensland have also been told to make sure their mobile phones are charged, and mobile battery packs if they have them.
Bureau of Meteorology forecaster Matthew Bass said the heaviest rain in southeast Queensland was still to come.
"Brisbane has already seen over 100mm is some areas," he said. "It does look like the heavy rain may just clear Brisbane by about midnight or the very early hours of the morning."
All schools closed
The Queensland government has taken the extraordinary step of closing all schools in Queensland between Agnes Waters and the New South Wales border.
The massive area stretches more than 600km down the state's coast. More than 2000 schools and childcare facilities are affected.
Queensland Deputy Premier Jackie Trad announced the last-minute decision just before 7.30am AEST on Thursday.
"The state disaster management committee has made the decision to close all schools in southeast Queensland between Agnes waters and the NSW border," she said.
"We have made this decision based on updated forecasts from the Bureau of Meteorology.
We know that the heavy weather conditions currently being experienced in southeast Queensland will intensify throughout the day."
Parents who had already taken their children to school were assured they would be looked after throughout the day and were urged to collect them before closing time if possible.
"If you have dropped off children, they will be cared for but please arrange to pick up your children earlier than the 3pm. School finish time. This includes independent schools and Catholic schools," Ms Trad said.
"We don't want parents to be - parents or children, to be on the road in this sort of weather. And that's why we have taken the decision to close schools."
The Deputy Premier also issued a warning that public transport could be closed down throughout the day, which could further complicate school pick-ups.
She assured: "We will care for everyone and make sure that nobody is left alone."
Students at the University of Queensland have been advised to put their safety first. While the university is open students will not be penalised for missing class today, a representative said.
The Queensland University of Technology has provided similar advice, saying staff and students don't need to come in.
In Brisbane, university and TAFE campuses were closing early, all the theme parks on the Gold Coast were shut and beaches along the entire south eastern coast from Mackay were also closed.
Virgin and Tiger Air flights into the Gold Coast are also to be cancelled from noon.
Brisbane has already recorded a month's worth of rain in 24 hours but the worst is yet to come, with authorities saying the heaviest falls will occur on Thursday afternoon and evening.
Worse than we thought
Police Commissioner Ian Stewart has admitted authorities don't know how serious the effects of today's deluge will be.
Following emergency meetings on Thursday morning, Mr Stewart said the aftermath of Cyclone Debbie was worse than anticipated.
"We had hoped that we had seen the last of Tropical Cyclone Debbie," he said.
"We knew it was going to be a low, we knew it was going to track exactly the way it did, what the sting is, though, that the intensity has ramped up."
Mr Stewart said Debbie's unexpectedly powerful resurgence had resulted in "unprecedented" rain and flash flooding.
"That's gong to continue right throughout today and it's slowly going to move down to track into this southeast corner," he said.
In Mackay, where flash flooding caused damage overnight, Mr Stewart said there had been a significant spike in 000 calls because people were in danger.
He urged people in the southeast to take precaution so that wouldn't be repeated.
"They were caught out, so we don't want that to happen," he said.
When asked to estimate the damage rains would bring today and overnight, Mr Stewart said: "We just don't know."
Sandbagging stations have been set up across Queensland's capital with residents of the state's most populous city warned to prepare for the worst.
Falls of up to 200mm or more across southeast Queensland will lash Brisbane in Cyclone Debbie's wake.
Southeast Queensland can expect about a month's worth of rain over the next 24 hours as ex-tropical Cyclone Debbie moves down the coast. "As the low tracks down the coast towards Brisbane we can expect falls of up to 200mm or more in southeast Queensland," a BOM spokesman told AAP. The Darling Downs, Granite Belt and Wide Bay region can also expect a lashing. Police Commissioner Ian Stewart urged Queenslanders to stay inside and not to underestimate the dangers of the heavy rainfall.
"We saw what happened five or six years ago when we had the summer of disasters," Commissioner Stewart said.
He encouraged parents to pick up their kids from school early before the worst of the rain hits.
Education Queensland have closed all schools in the southeast of the state.
Premier Annastacia Palaszczuk is returning to Brisbane from the northern cyclone strike zone to meet with emergency services to plan for the state's latest disaster.
The city's is currently open and operational, but the Brisbane Airport Corporation has warned that the rain event has potential to interrupt scheduling, and travellers should expect delays and cancellations throughout the day.
TransLink has announced public transport in southeast Queensland will be free from 10am AEST.
Severe thunderstorms are likely to produce very heavy rainfall that may lead to flash flooding over the next several hours. Locations which may be affected include the McPherson Range, Springbrook, Numinbah Valley, Little Nerang Dam, Tallebudgera and the area south of Canungra. 186mm in 3 hours has fallen at Numinbah.
Numinbah has already seen 287mm today and Springbrook on the Gold Coast has seen 237mm.
Disaster teams and dam operators are on high alert, swiftwater rescue reinforcements are arriving from interstate and sandbags are ready.
Senior meteorologist Matthew Bass from the Bureau of Meteorology said rainfall totals could exceed 400mm throughout the Gold Coast and Sunshine Coast Hinterland.
Mr Bass said rainfall and thunderstorms brought by ex-tropical Cyclone Debbie would hit Brisbane, the Gold Coast and Sunshine Coast areas today, moving across the area tonight and offshore Friday morning.
Areas of the Gold Coast Hinterland have already been lashed with up to 130mm of rain in only three hours on Thursday.
The Bureau of Meteorology has issued a severe thunderstorm warning for southeast Queensland and both Brisbane and Sydney are forecast to cop a drenching today as ex-Cyclone Debbie drags a humid tropical air mass south.
Officials say the Gold and Sunshine Coast hinterlands, where up to 650mm of rain has fallen already this month, again face the biggest soaking.
The southeast's overall dam levels were at 71.7 per cent yesterday, but are set to rise substantially.
Some, like the Gold Coast's Hinze Dam, were already spilling over after last week's torrential rain and Seqwater said this week's downpour could add several months' water supply to the southeast.
The low pressure system is expected to move off the coast tomorrow morning as coastal areas prepare for big seas.
On the Gold Coast, classes have been cancelled at Griffith and Bond universities, and elective surgeries are cancelled at the Gold Coast University Hospital.
Dreamworld is also closed for the day.
New South Wales
NSW residents can expect to be lashed by heavy rain in the afternoon as the remnants of ex-tropical cyclone Debbie clash with a cold front. The Bureau of Meteorology is forecasting heavy showers and flash flooding in the state's northeast and damaging coastal winds north of Sydney on Thursday and Friday.
Residents in Lismore, Grafton, Coffs Harbour Glen Innes and Inverell will be dumped with most of the rain while Sydney, Gosford, Newcastle and Port Macquarie will be hit by damaging winds.
The Northern Rivers region can expect 100mm over a 24-hour period. Sydneysiders can expect showers to start on Thursday afternoon and continue into the evening with a maximum of 45 millimetres expected.
"It is likely that some locations will exceed more than 200mm," the bureau said on Wednesday.
The showers will linger on Friday for Sydney but it won't be as much as the previous day's dumping, with about 6mm forecast.
Cyclone Debbie's damage up north
Severe weather warnings have been cancelled across central and northern Queensland where the wrath of ex-tropical Cyclone Debbie has passed as it makes its way south.
Though the worst of the damage has been done, recovery efforts continue to be hampered by extreme weather.
Emergency workers said a dramatic rescue operation underway in the Pioneer Valley, west of cyclone-battered Mackay in north Queensland, is being hindered by bad weather.
A number of people remain stranded in flood waters near Mackay and authorities say they can't yet say how bad the situation is.
"We saw a sudden increase in calls for service to emergency services. Our resources were deployed into the field. A number of rescues were undertaken and are still being undertaken," Queensland police Deputy Commissioner Stephan Gollschewski told reporters.
"A number of people have been safely rescued, however, it continues. This is a very difficult operating environment. We do not have complete understanding of what is happening." Two helicopters are involved in the rescue effort.
At Airlie Beach, locals are scrambling for supplies after Woolworths opened its doors for the first time since Cyclone Debbie descended on the coastal town.
Airlie Beach - one of the worst-affected areas - remains largely in lockdown as emergency services try to repair fallen power lines and roads following Cyclone Debbie.
Businesses will be unable to reopen until the power is reconnected. Two restaurants opened for brief periods on Wednesday to cook up meat and seafood that had to be used.
Queensland Fire and Emergency Services Commissioner Katarina Carroll said there was concern for 20 to 30 people, including at Eton, on the Pioneer River. Police Commissioner Ian Stewart said there had also been rescues in Mackay overnight.
Ms Carroll said weather conditions were "horrendous" last night with very heavy rain and strong winds.
"Today we managed to get helicopters into the air. Communications have been extraordinarily difficult. While we are extremely confident that quite a few rescues have been made, we are going back, obviously, to see," she said.