More dangerous wet weather is being forecast for NSW, including an east coast low bringing heavy rain and possible flash flooding, the Bureau of Meteorology (BOM) has warned.
Emergency services have been busy in parts of Sydney, including the Hawkesbury-Nepean, Richmond, Menangle and Windsor, and more major flooding is forecast for the area.
Flood rescues had to be carried out after more than 100 millimetres was recorded on Saturday at North Richmond, and a landslide at Kiama on the South Coast, after around 68 millimetres fell in an hour.
"We are facing, unfortunately, a few more days of ongoing wet, stormy weather which will be quite dangerous for residents of NSW," BOM meteorologist Jane Golding said.
The BOM would be closely monitoring the low to see where it forms off the coast, and residents were urged to carefully monitor warnings, Ms Golding said.
"We know east coast lows, they're dangerous weather systems, we know the devil is in the detail of where exactly they form off the coast, and this system hasn't developed into an east coast low yet — as it does we will be fine-tuning the warnings," she said.
In the north of the state, the Clarence River remains at a major flood level as residents of the Northern Rivers clean up after last week's devastating floods.
Ms Golding said the Northern Rivers region could expect thunderstorms with large hailstones, damaging winds and heavy rain, but the storms would be more "hit and miss" than widespread.
There are currently four confirmed deaths in the region with a number of people still "unaccounted for".
NSW Police Superintendent Scott Tanner said it was impossible to give an exact number because in some cases people may "no longer be at their place of residence".
"What we are asking for is that if you have been impacted by the flood and if you have not either registered your details or contacted emergency services to let them know you're safe, please do so," he said.
"We are asking for the community to help us because we do have a lot of resources up here that are tracking the data to make sure that we've not left anyone behind."
The east coast low is expected to develop over the next two days and is expected to impact an area from the Bellinger to Shoalhaven, including Sydney and the Hunter, Ms Golding said.
On Monday the focus would shift to include the Hunter and mid-north coast where river levels remain high around Maitland, Singleton, Dungog, Gloucester, Wingham and Taree.
Ms Golding said on the bright side, the severe weather appeared likely to clear from Wednesday onwards.
State Emergency Services (SES) Commissioner Carlene York said the focus had been on assisting people in Penrith, the Hawkesbury and Mount Druitt, and on trying to clear evacuation orders in the Northern Rivers.
She said the SES was helping people in the Hunter and Mid-North Coast prepare for further bad weather, and the community needed to understand the danger had not yet passed.
"We have had five fatalities and I don't want any more," she said.
"It's still dangerous out there, the weather is still continuing."
The SES has had over 15,000 calls for help and made 700 flood rescues, with 26 of those just last night.
Hundreds of volunteers from other states have come to assist, and helicopters operated by the Australian Defence Force (ADF) and Rural Fire Services (RFS) are dropping essential supplies to communities.
Meanwhile in Huonbrook, inland from Brunswick Heads on the north coast, residents are still completely cut off due to major landslides.
There are network outages and phone and internet services are also down, exacerbating their isolation.
Locals and those in surrounding areas are communicating with each other via two-way radios and checking in with each other regularly.
Trying to reach family, friends and services beyond their area is impossible, so people are either hiking to find reception or communicating through those bringing help and supplies.
Among those helping out is Brunswick Heads resident Fraser Walker — he bought a satellite for himself but knew it was desperately needed elsewhere.
Mr Walker said they were desperately trying to find more satellite internet to take to trapped residents who could go without connectivity for some time.
"What we want to achieve is one centralised location in these cut off areas that can have the link to the outside world," he said.
Volunteers like Fraser have been largely responsible for getting supplies to affected residents all over the Northern Rivers, and there are calls for the government to help with coordination and ensure these civilian-led missions are carried out safely.
"We really need to keep people in contact until someone from a government agency can come in with a plan and say 'this is what's happening, you guys need to evacuate, you guys are OK to stay'," he said.
"It's not up to those everyday volunteers to make those decisions on behalf of [residents]."
