Three people have died in floodwaters in Queensland.
A man, woman and young child lost their lives, reportedly after their car was swept off a flooded road in Caboolture, north of Brisbane.
Queensland Premier Annastacia Palaszczuk described it as a tragedy.
Queensland and New South Wales residents had previously been urged to take care amid weekend forecasts of more damaging storms.
In Queensland, the Bureau of Meteorology (BOM) issued a severe storm warning for the south-east of the state.
Heavy rain and potential flash flooding is expected over areas from Bundaberg to Dalby and Stanthorpe.
The BOM has warned that dangerous, slow-moving thunderstorms have been detected on weather radar and flood warnings remain in place for several areas.
The heavy rain has also slowed operations at Brisbane Airport, where delays are expected.
Queensland Premier Annastacia Palasczuk said the government would remain in constant contact with the bureau, urging residents to be cautious.
"If you do not have to go outside tonight, please don't,” she said.
Rain and thunderstorms expected to intensity in NSW
The BOM has also issued warnings for NSW, where heavy rain and thunderstorms may lead to flash flooding, with the wild weather expected to peak early Saturday morning.
Damaging winds with gusts up 100 km/hr are expected to pick up tonight on the Northern Rivers and northern parts of the Mid North Coast forecast district.
The BOM has warned coastal areas are the most vulnerable, while elevated parts of the Northern Tablelands may also see wind gusts to 90 km/hr.
Meanwhile, SES volunteers helping storm-ravaged NSW have had their vehicles broken into.
SES workers in the Hunter region woke on Friday to find chainsaws, power tools, helmets and even a car fridge had been stolen from their vehicles overnight.
Some of the equipment has SES branding on it, police say.
It's the second robbery SES volunteers have had in the past week.
