NSW coastal communities are being warned to brace for heavy rain and flash flooding as a wild weather system forms off the east coast.
The NSW State Emergency Service (SES) has told people in several large population centres to prepare for thunderstorms that will start early on Sunday and continue into next week.
In a statement, the SES said the system was expected to develop "somewhere between the Mid-North Coast and South Coast" and may result in " intense periods of heavy rain, strong winds and hazardous surf conditions".
Bureau of Meteorology (BOM) duty forecaster Helen Kirkup said the Illawarra and South Coast were likely to see the worst of the system early on Monday.
She said those areas were "at risk of the heavier rainfall and the gale force winds" if an east coast low developed.
Ms Kirkup told people spending the school holidays on the South Coast they should monitor weather developments tomorrow.
"When these systems do develop, if you're likely to be anywhere near the coast it's important to monitor the local alerts," she said.
She said although most of the coast will receive some rainfall Sydney's metro area was unlikely to get "intense rainfall".
Tony Day, from the SES, said the weather system was likely to be unpredictable, and that people should prepare for flash flooding.
He said emergency responses during severe weather events were further complicated by NSW coronavirus restrictions.
"The current COVID-19 environment presents additional considerations for emergency services in responding to severe weather events," Mr Day said.
"So the most practical way the community can help should the heavy rain eventuate is to avoid all non-essential travel and to never drive, ride or walk through floodwaters."
East coast lows often intensify rapidly over a period of 12-24 hours, making them one of the most dangerous weather systems to affect the coast, according to the BOM.ABC