Southeast Queensland is shutting down, with swift water rescues playing out across the region as ex-tropical cyclone Debbie dumps a staggering amount of rain.
Emergency crews have had to save people from cars trapped in floodwaters in Brisbane, and on the Gold and Sunshine coasts, where some businesses and roads have been flooded.
On the Sunshine Coast, crews are working to save a couple and their four children, whose home has been swamped by fast-rising floodwaters at Tanawha.
A boat is currently trying to reach the family.
Meanwhile, another house is in danger of going under in the Scenic Rim area, inland from the Gold Coast.
An unknown number of people are trapped in a house there that's inaccessible by road, and authorities are deciding whether to send in a chopper.
The SES says people have been rescued from cars caught in floodwaters in Brisbane, further south at Logan, and on the Gold and Sunshine coasts, as the region braces for the worst of the rain which is expected from about 3pm local time.
The SES has received 2800 calls for help across the state, with the number steadily rising, particularly in the southeast where people are desperately sandbagging their properties, and calling for help with leaking roofs.
Queensland Fire and Emergency Services commissioner Katarina Carroll said emergency services were braced for many more calls.
"Whilst it's looking pretty horrendous out there, it's going to get worse," she said.
She warned that as the weather worsens, emergency crews may not be in a position to rescue people.
"We will respond for as long as we can, but there will become a point later tonight where we mightn't be able to."
The Queensland government has taken the unprecedented step of closing all of the 2000 schools across the southeast, as roads go under.
Public servants have also been sent home for the day and public transport, which has seen delays, is free to encourage people to return to their homes before the worst of the weather arrives.
In Brisbane, there's been significant flooding in East Brisbane, Moorooka and Greenslopes. The city's universities have closed their campuses.
On the Gold Coast, flash flooding is occurring in many places and its iconic theme parks are closed. Every beach from Mackay south to the NSW border has been closed.
Virgin Australia has cancelled domestic flights at Queensland's Gold Coast and Prosperine airports, while no Qantas flights will operate to or from Gladstone.
Damaging 100km/h hour winds are expected to develop on Thursday afternoon, amid soaring rainfall tallies.
Some parts of Brisbane have had more than 100mm of rain since 9am. By comparison the city's average March rainfall figure is 110mm.
The weather bureau has warned the southeast could see falls of 400mm in 24 hours and Police Commissioner Ian Stewart has warned it could even go beyond that.
"I think we've got to be careful that we're not sending a message that you might have 400 or 500 millimetres of rain in a particular area. It could actually happen everywhere," Mr Stewart said.
The premier has returned from cyclone-ravaged north Queensland to deal with the southeast's weather crisis. She will update the media shortly.
The SES later said the family at Tanawha had been rescued, including four children aged 11 months to nine years.
Their father, who has a broken back, has stayed at the house because he can't be moved but has medication and food supplies to last a few days, a rescue worker has told the Nine network.
Meanwhile, the Gold Coast City Council has opened three evacuation centres for vulnerable residents, at Helensvale, Robina and at Nerang.