An "astronomical" amount of rain has drenched parts of Queensland with Wide Bay and the Sunshine Coast seeing a month's worth of rain in an hour and evacuations have been ordered in Lockyer Valley.
The Bureau of Meteorology (BOM) said a coastal trough came onshore overnight and the peak of the system was forecast to hit on Friday and into Saturday.
Old Range Road, north of Biggenden, received 161 millimetres in the hour before 4am and 423mm in three hours.
Paradise Dam recorded 75mm in 30 minutes while Hills Road, near Seventeen Seventy, recorded 142mm in the hour to 5am.
BOM forecaster Brooke Pagel said in the 24 hours to 9am, Gayndah in North Burnett received 463mm, "the highest total in Queensland", followed by Pomona, on the Sunshine Coast, which received 450mm.
Forecaster Felim Hanniffy said the rainfall totals were "astronomical" and the Sunshine Coast could see "a repeat performance" of the falls that triggered widespread flooding earlier this week as the system moves slowly south.
Life-threatening flooding, rapidly rising rivers
Meteorologist David Grant said heavy rain will continue across south-east Queensland, as far north as Hervey Bay to the Gold Coast, until Saturday.
"Since many catchments are saturated, there is a high risk of dangerous and life-threatening flash flooding," he said.
"This could also lead to local landslides during the cause of this event.
"We have a major flood warning now current for the Mary River, with Gympie expected to exceed the major flood level and exceed levels that have not been seen since February of 1999.
"Major flood warning is also current for the Logan River, with Beaudesert expected to exceed the major flood levels sometime during the course of Saturday."
Mr Grant said there were also major flooding warnings for the Murray River, Logan River, Laidley Creek and Lockyer Creek.
Helicopters sent to rescue residents on roof
Deputy Commissioner Steve Gollschewski says a helicopter has been deployed to rescue the six Grantham residents on the roof.
"There are problems with the weather, we're not certain it will be able to fly into that area," he said.
"We are also looking at other options to get other aerial assets in there to assist these people.
"We do have resources including QFES resources on the ground, and we will advise as that unfolds."
Conditions expected to worsen
Deputy Premier Steven Miles said the severe weather was expected to worsen.
"Indications currently are that the rain over the next 24 hours could be even worse than was expected this morning," he said.
"It may intensify and go for longer into tomorrow.
"These catchments are already saturated so particularly places like Gympie and Maryborough that flooded not that long ago, the Mary River is rising very quickly."
More than 650 calls for help
QFES state coordinator James Haig told ABC Radio Brisbane authorities had crews in place to respond to the Gympie flooding.
"We've had over 650 requests for assistance, lots of them through the SES, but we've also had a number of water-based rescues that are operational across the whole area," he said.
Mr Haig said the fact that catchments were already completely saturated before this major rain event was contributing to the rapidly escalating flood situation across south-east Queensland.
The occupants of about 20 homes at Withcott, Helidon and Grantham in the Lockyer Valley have been asked to evacuate as floodwaters rise.
Lockyer Valley Mayor Tanya Milligan said emergency services were preparing for the possibility that up to another 200 millimetres of rain could fall in the next 24 hours.
She said people in flood-affected areas of the Lockyer Valley who could safely leave their homes should do so.
"We certainly encourage people to go to friends and family and if there isn't friends and family, then [the] council will take it from there."
In the Lockyer Valley, Mr Haig said there had been rapid rises in stream levels, with several water-based rescues and "significant rainfall" over the Toowoomba Range and into Toowoomba.
Businesses in Gympie are evacuating following three days of heavy rain.
Queensland Police Service Deputy Commissioner Steve Gollschewksi said authorities were preparing for riverine flooding, particularly in the Mary River.
Wayne Luck, who owns a psychology clinic in the CBD, said it appeared the flood was the biggest they have ever seen.
"That's quite likely to be in excess of 18 metres," he said.
"This building here that we're in, the last time it flooded like that it was up to the ceiling.
The North Burnett, Noosa, Gympie, Toowoomba and Lockyer Valley councils have issued emergency alerts urging residents to stay off the road due to a risk of flash flooding and a possible impact to bridges.
In the Maryborough region, Fraser Coast Mayor George Seymour said there will be a minor flood peak in the town tonight ahead of a second peak in a few more days as the torrent flows from Gympie.
The council said Granville residents need to be prepared to be cut off from Maryborough "for potentially several days".
Queensland Fire and Emergency Services deputy commissioner Mark Roach said the public knew the weather event was coming and should not be on the road.
"It is a life-threatening event and we've seen that from the outcomes over the last couple of days," he said.
The floodwaters have already claimed the lives of two people this week.
Swift-water rescues in Lockyer Valley Region
Swift-water rescue teams have saved three people from rising floodwaters at Helidon in the Lockyer Valley after their car was caught in the dangerous waters.
Two people were found clinging to the roof of the car, while the third person was found nearby in the water. A fourth person made it to safety on their own.
Among those rescued were Helidon residents Jean and Lloyd Warr, who became trapped in their car after their house became inundated with about three feet of water.
Ms Warr said they left home to search for safer ground.
"We thought … we can go to the cemetery because the Catholic cemetery didn't go under [in the 2011 floods]," she said.
"We thought we'd save ourselves. And we didn't make it. We climbed out and sat on the top of the car."
Localised flooding has forced road closures around the Darling Downs, including a major road connecting the Toowoomba Range to the Lockyer Valley.
Toowoomba's Officer in Charge of Highway Patrol Senior Sergeant Kim Hill said the Toowoomba Connection Road was cut in both directions at Withcott due to flooding.
"I believe there's [also] some challenges and some water rising around the roads along the Warrego Highway around the Lockyer Valley so please be mindful when you're travelling those directions," she said.
She said police and other emergency services had received a "significant" number of calls for help from members of the public attempting to cross floodwaters.
Water grid at highest level in three years as Brisbane, Moreton Bay cop soaking
Up to 150mm was expected to fall on Friday, with up to 200m in Mount Glorious and parts of the north-west.
Ms Boekel said it was a "watch and wait situation" for the Brisbane River and low lying areas that were set to be inundated.
"We really do need to see what happens for the rest of today and overnight tonight to see where the peaks will be along the Brisbane River and exactly how affected Brisbane City will be," she said on Friday.
Wivenhoe Dam, which supplies Brisbane's water, has reached 60 per cent capacity, the highest level since 2019.
Overall, the south-east Queensland water grid is sitting at 72.6 per cent, its highest level in three years.
Moreton Bay Mayor Peter Flannery said the region was saturated and more than 50 roads cut so far.
He said Moreton Bay council libraries were open as places of refuge, and evacuation centres were prepared to open across the region if needed.
The coastal trough which is bringing the intense rain has been building off the coast for the better part of this week.
On Friday morning it was sitting roughly between Seventeen Seventy down to Gayndah and into the eastern parts of the Darling Downs.
'Cut off for days'
Summa Court said the intense rain started about 3am at her home in Federal, north of the Sunshine Coast.
The family had moved a caravan to higher ground earlier this week and relocated there when the local creek rose to within 30 metres of their house.
"We're well stuck here for a few days," she said.
On the Scenic Rim, Mayor Greg Christensen said about 200 people could be stranded after the Upper Coomera Road-Flying Fox Road in Ferny Glen was washed out.
"[They will be isolated] and will be for some days — we're trying to understand what the urgency of needs is so we can plan to try to help them," he said.
Mr Christensen urged people not to leave their homes unless it was urgent after some localised landslips.
