The NSW premier has apologised to flood-devastated communities, as vast swathes of the coast prepare for more heavy rain that could cause major flooding in already saturated parts of the state.
Heavy rainfall and thunderstorms are predicted to continue smashing the coast, posing a renewed flood risk for multiple river systems from northern NSW to the state's south coast.
The heaviest falls are forecast for Greater Sydney and the Hunter region however moderate flooding is also forecast for the Northern Rivers, Mid North Coast, South Coast, the Illawarra and Bega.
Dominic Perrottet said sorry to thousands of people in the Northern Rivers district, whose homes and businesses were destroyed when towns like Lismore and Ballina were inundated by floodwaters last week.
Many had to be rescued by fellow citizens and have since struggled to access basics such as food, water, power, fuel, phones, ATMs, the internet and medical supplies.
"I'm very sorry ... but we're doing everything that we can," Mr Perrottet told the Nine Network from Lismore.
"Some of those areas will look back at this and say it could have been done better but ... we're doing absolutely everything we can to provide care and support for those who need it to get those essential supplies in," he said.
The emergency response would be reviewed, he added.
Floods have claimed six lives in NSW, including four in Lismore.
The Australian Defence Force is helping with the mammoth clean-up with 512 personnel on the ground in NSW.
Some 5000 personnel will be put on task or made available in NSW and Queensland over the course of this week, as 2010 are on the ground in both states, the ADF said.
"We're getting supplies in. We're getting food in," Mr Perrottet said.
Around 2000 of the 3500 homes assessed so far in the Northern Rivers are no longer habitable, increasing the need for short-term and medium-to-long-term accommodation.
Telstra on Monday said it had restored about 80 per cent of mobile coverage for communities in northern NSW and 75 per cent of landline connections.
But some areas remained inaccessible due to continued flooding, road damage or a lack of electricity that is hampering the work of around 1000 technicians.
The northern NSW communities of Kingscliff, Main Arm, Mullumbimby, Ocean Shores, Tucabia, Uki and Wooli are among those still having issues with communications.
The State Emergency Service had another 550 calls for help overnight and performed nine flood rescues.
SES Deputy Commissioner Daniel Austin says volunteers are waiting with "bated breath" to see what Monday brings.
"We're certainly on high alert from the Mid-North Coast down into the Shoalhaven," he told the Nine Network.
"We are watching exceptionally closely a number of catchments ... around the Hawkesbury and Central Coast and places.
"The water hasn't retreated yet. We're now going to see more flooding on top of what we've already seen."
Renewed flooding is likely in the Hawkesbury-Nepean Valley and major flooding continues in the Upper Nepean, Nepean, Hawkesbury and Colo Rivers, the SES said on Monday.
Rainfall on Monday and Tuesday could push the Nepean River at Penrith over six metres causing minor floods.
At Wiseman's Ferry the Hawkesbury River was flooding at moderate levels on Monday morning and is likely to rise over the major flood level of 4.2 metres on Monday evening, and up to 4.4 metres through to Tuesday.
Major flooding is also taking place at North Richmond and is likely to happen at Putty Road as the Colo River is expected to exceed 10.7 metres on Monday night and continue to swell to up to 11.5 metres on Tuesday.
Rain is causing significant travel delays with cancellations expected on most Sydney Trains, NSW TrainLink Intercity and Regional train services and drivers are being urged to stay off the roads unless it's absolutely necessary.
