Torrential rain in the state's southeast caused flash flooding, water rescues and hundreds of calls for help on Thursday, and several schools were forced to close on Friday.
The Bureau of Meteorology is now warning of severe thunderstorms, heavy rain and flash flooding across South Australia, Victoria, NSW, Tasmania and again in Queensland at the weekend.
In a video update on Friday, Senior Meteorologist David Crock said scattered showers and thunderstorms were continuing across central Queensland, through the state's southeast and into northern NSW.
Attention on Saturday would shift to the southern states, where a trough system would be the focus of severe storms, possibly through parts of South Australia and Victoria, he said.
That would push further into Victoria and Tasmania by early Sunday and then bring significant severe thunderstorm outbreaks through the ACT, western NSW and southeast Queensland into Monday.
The fringes of Melbourne and the northern and eastern suburbs could see a severe thunderstorm on Saturday afternoon, Mr Crock said, but Sydney was less likely to cop storms.
The bureau was forecasting severe thunderstorms, with damaging winds, large hail and heavy rain possible across a large area including Canberra, western NSW and western Queensland.
Later on Monday, the trough system would push off the coast into the Tasman Sea, giving southeast Australia more settled weather from Tuesday.
Even in the absence of severe thunderstorms, heavy rain could quickly lead to flash flooding in already-soaked parts of Queensland, Mr Crock said.
Severe thunderstorms were again possible for Brisbane and the Gold Coast and much of southeast Queensland on Sunday, he said.
"Looking ahead to Monday we're already forecasting severe storms likely through the northern rivers of New South Wales and up into parts of southeast Queensland as well."
The bureau on Friday still had flood warnings in place across southeast Queensland.
Thursday's heavy rain stretched from Caboolture down to the Border Ranges, with some places copping well over 200mm falls.
The Queensland Fire Department carried out more than 16 swift-water rescues, including using a raft to retrieve an elderly man clinging to the roof of his vehicle at Caboolture.
A truck driver drove into floodwaters at Goondiwindi to pluck a stranded driver from his vehicle, while another driver at Petrie was rescued by community members.
An ABC reporter and bystander swam to save a trapped man before his car submerged at Morayfield.
Many roads remain closed by floodwaters and amid the downpours the State Emergency Service responded to more than 540 call-outs.
The City of Moreton Bay is urging residents to stay alert this weekend, with more showers forecast and many creeks still running high.
"Short bursts of heavy rain have potential to cause flash flooding quickly and with little warning," it said in a statement.
Parts of the city received more than 270mm of rain in 24 hours, with intense falls on Thursday morning causing flash flooding and road closures.Â
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