About 2,000 people are being evacuated from their homes on the New South Wales far north coast, after the same weather system that drenched Queensland moved south.
Major flooding is expected in the Tweed Valley after receiving more than 500 millimetres of rain over the past three days with more on the way.
Up to half that much again is forecast for the next 24 hours.
A major flood warning is current for the Tweed River, which was predicted to exceed the major flooding level at Murwillumbah at 6pm (AEDT). The river is expected to rise to around 5.2 metres by 8pm (AEDT).
Evacuation orders have been issued for South Murwillumbah, Condong, Tumbulgum and Chinderah.
The nearby village of Fingal Head is also being evacuated.
SES spokesman Simon Gregg says people should take heed of the evacuation order.
"The reason we've gone with the evacuation order now is so that there is time for people to be spoken to," he said.
"It normally takes a period of time for it to sink in with the residents, and then they decide that they're going to evacuate."
Minor to moderate flooding is expected in other catchments on the Northern Rivers.
Warnings for minor to moderate flooding are in place for river valleys further south between Brunswick Heads and Taree.
Residents downstream from the Clarrie Hall Dam at Doon Doon Creek and Uki are being asked to prepare for possible evacuation.
The situation has eased on the mid-north coast, but more rain is expected and several communities remain isolated.
Police are urging people in the region not to drive after many drivers have been ignoring safety warnings.
"Throughout our region all day we've had calls from people who have been either washed off the road or stuck on causeways throughout the district," Inspector Jim Kain said.
"On many occasions they're in areas that we just cant get to or it stretches our resources, takes us away from other areas such as those evacuations to make sure these people are all right."
A free-call telephone service has been set up to provide information for flood-affected residents - 1800 227 228.
The call centre is staffed by emergency service workers and volunteers.
Those seeking emergency assistance should still call the SES hotline on 132 500.
- Australian Broadcasting Corporation
- © ABC