A severe weather warning for wild surf, damaging winds and heavy rainfall has been issued from Sydney to the South Coast, and residents of Moruya CBD and Sussex Inlet are evacuating due to flooding.
The NSW State Emergency Service issued the urgent evacuation order to residents of Sussex Inlet at 3:30pm and Moruya's CBD at 5:00pm on Sunday.
Floodwaters are rising along the Moruya River, which is expected to reach moderate flood levels and peak on Sunday night.
The Bureau of Meteorology said a deepening trough with several low centres was bringing heavy rain from the South Coast to the mid-north coast of NSW.
Riverine flooding is expected to continue throughout the Illawarra this evening, while areas of Sydney, the Blue Mountains and Newcastle may see flash flooding.
Dangerous winds of more 90 kilometres per hour are expected to pummel the coastal fringe of the Illawarra, the South Coast, Sydney and the Hunter before easing overnight.
Monday will bring renewed force from the system, which the bureau warned would strengthen before heading to the mid-north coast by the afternoon.
Since 7:00pm on Friday, the SES have received more than 690 calls for help across NSW.
An SES spokeswoman said that included about 29 flood rescues, many of which had been around Goulburn, Nowra and Wollongong.
She said most South Coast residents at risk of flooding danger had been alerted of the evacuation order by SES workers.
"Our volunteers have been on the ground doorknocking to warn residents to evacuate," an SES spokeswoman said.
Homeowners on the state's central coast are bracing for further coastal erosion as waves which are expected to exceed five metres smash the shorelines.
"Surf conditions should ease in the south later Monday, and hazardous surf conditions should persist along the northern coast Tuesday," the weather warning read.
Two east coast lows have caused significant erosion on the NSW coast in July, with many families forced to leave their homes.ABC