Heavy rain across southeast Queensland and the north of NSW has prompted flash flooding warnings as authorities answer hundreds of calls for help.
Some areas in the Gold Coast and northern NSW border recorded more than 350mm of rain since Saturday with warnings there is more to come.
Streets in Coffs Harbour and Tumbulgum flooded.
Four people were rescued from floodwaters in NSW overnight and about 20 caravaners were moved to higher ground.
NSW State Emergency Service received 700 calls for assistance.
Authorities say more heavy rain, damaging winds and king tides are likely from Fraser Island to Port Macquarie throughout Sunday.
Motorists are being warned to stay off the roads and not to attempt to drive into any floodwaters.
The Bureau of Meteorology has also issued a flood warning for southeast Queensland.
In NSW flooding is likely in the Northern Rivers and Mid North Coast areas, with further heavy rainfall up to 100 to 200mm expected.
“This is a dynamic weather system and you should always expect the unexpected,” BOM hydrologist Justin Robertson told reporters.
Gale wind warnings are forecast for the Byron coast and strong wind warnings are in place for the Coffs and Macquarie coast. The gale warnings are forecast to last into Monday.
The BOM says that while heavy rainfall in the Tweed Valley and Queensland border may ease on Sunday during the day, it is expected to become severe again on Sunday evening and into Monday morning.
“We are really appealing to residents in the Mid North Coast and Northern Rivers to stay vigilant, monitor your local conditions and local forecasts and stay out of floodwaters,” NSW SES assistant commissioner Dean Storey told reporters.
Rough seas and wild surf are forecast north from Ballina, with waves of more than five metres tipped from early Monday.
All Gold Coast beaches have been closed along with the majority of Sunshine Coast beaches.
“The combination of damaging surf and abnormally high tides may lead to significant beach erosion north from about Ballina,” the BOM warns.
Upper Springbrook in the Gold Coast hinterland recorded 475mm of rain overnight and Couchy Creek, near the Queensland and NSW border, received 365mm of rain since 9am on Saturday, with Numinbah recording 348mm and Chillingham 306mm.
Flood warnings have been issued for the Tweed, Bellinger Brunswick Rivers and Marshalls Creek.