Emergency crews are preparing for more heavy rain in northern New South Wales.
The water levels are expected to rise quickly because of the already saturated catchment areas after recent floods.
Dimitri Danchuk from the Bureau of Meteorology says a slow-moving tropical low is bringing the latest rain.
"It hasn't moved much. It's off the south-eastern Queensland coast but there are signs that it's started a gradual approach to the far north coast," he said.
"It is likely to make landfall at some stage in the early hours of Friday."
The bureau has issued a flood watch for all coastal river valleys from the Hunter north to the Queensland border, saying there is a 75 per cent chance of flooding over the next few days.
Late yesterday the State Emergency Service had to rescue two tourists who became trapped on the wrong side of a swollen creek near Nimbin.
The pair had been isolated since Monday and called triple-0 for help after their food began to run low.
The SES says it has deployed around 130 extra volunteers to the state's north in anticipation of the approaching weather system.
The weather bureau says there could be local falls of over 200mm.
Coffs Harbour SES spokesman Bill Roffe says sand is being piled in local parks for people to fill their own sandbags, less than a month after the area's last flooding.
"For this one we're actually doing a fair bit of preparation we had done since Australia Day anyway," he said.
"We did a lot then, we're doing even more now for what is about to occur.
"If people can self-help, fantastic. The other thing we'll be doing today is we have about six points around town where we drop sand bags."
Further north, Tweed Shire Council planning and infrastructure engineer Danny Rose is also urging people to prepare.
"They need to start thinking about moving their cars and other valuables to higher land or higher areas within their property and they mostly need to be prepared to move if the SES start ordering evacuations or other response measures," he said.
© ABC 2013
17:01 EST Sydney's offshore Sea Surface Temperatures (SST's) have remained above 21 degrees for the last four days.