The saturated catchments of the Illawarra, Southern Highlands and South Coast are bracing for a second east coast low in less than a week.
Across the region in the past seven days 112 millimetres of rain has been recorded at Bellmabi, 344 at Kiama, 230 at Moss Vale, 350 at Nowra and 362 at Wollongong.
Dean Narramore from the Bureau of Meteorology (BOM) said the latest east coast low developing over north-eastern NSW was shifting south and would move off the mid north coast tonight and rapidly deepen.
Of particular concern, he said, were the already saturated catchments, with many minor to major flood warnings on river systems along the coast.
"We are expecting rainfall of 50 to 150 millimetres especially through coastal areas and elevated terrain and especially near and south of where this low tracks."
Residents in parts of Sydney's south-west have also been ordered to evacuate ahead of another night of heavy rain.
Earlier today, Premier Dominic Perrottet said 2,000 homes had been deemed uninhabitable by the record floods.
Heavy rainfall will persist throughout the area on Monday evening and into Tuesday.
The BOM warns the rainfall also increases the potential for landslides and debris across roads.
Damaging wind gusts with peak gusts of around 90kph are possible on Tuesday over the South Coast, Illawarra and Southern Tablelands.
A separate severe weather warning for damaging and hazardous surf is also current for Illawarra coast, Batemans coast and Eden coast.
History of east coast lows
Usually a winter event, the BOM's records point to the five east coast lows occurring during June 2007 as "a rare, if not unprecedented sequence".
The 2007 event created sustained heavy rain, flooding, strong winds and large ocean waves and swell that caused the coal carrier Pasha Bulker (76,741 tonnes) to run aground at Nobby's Beach in Newcastle.
In the Illawarra, an east coast low caused moderate rainfalls there and along the South Coast in October 2004.
In August 1998, another east coast low generated falls of more than 300 millimetres in the Illawarra, the highest being 401mm at Kangaroo Valley.
Landslips impact road and rail
The weather events of the past week have caused multiple road slips, with the worst impacting the Kiama Bends on the Princes Highway.
On Wednesday, the first landslip was reported on the Bends causing the temporary closure of the highway; on Sunday, a second landslip occurred 700 metres away.
Just before midnight on Sunday, a landslip also closed the rail line between Minnamurra and Bombo. There were 15 passengers on the train at the time but no injuries were reported.
Local MP Gareth Ward has called for Kiama, Shoalhaven and Shellharbour to be declared natural disaster areas.
He also plans on raising the need to improve the Princes Highway at the Kiama Bends when state parliament returns.
Picton on high alert
For almost a week, the Picton CBD has remained under an emergency evacuation warning because of rapid rises in Stonequarry Creek.
Last Wednesday and Thursday local businesses, supported by the SES and council, sandbagged the main street after the first warning was issued.
A second evacuation warning was issued on Saturday after heavy rain fell, leaving the town on high alert.
The warning remains in place as the river rose to almost six metres at midday on Monday after heavy falls.
Wollondilly Mayor Matt Gould said travel around the shire would be increasingly difficult over the next few days as the area braced for more intense rain and possible flooding.
"It will mean that our bridges will be cut off again," he said.
"For the villages of Warragamba, Silverdale and Werombi, there is the possibility that if we do get that kind of rain that they could become temporarily isolated.
"In the far west of the shire, our remote village of Yerranderie is completely cut off and we have been talking with the SES around resupply for the residents as needed."
Cr Gould also praised the resilience of his community as it faces another flood threat.
He said while the current weather event brought back memories of the 2016 flood disaster, the community remained strong.
"From our RFS volunteers, our SES volunteers, the numbers of people, random citizens that have been sandbagging or helping to fill sandbags.
"The number of people that have been offering lounges to sleep on or spare bedrooms to complete strangers, we just really do come together."
