Thousands of people on the NSW south coast have been warned to stay indoors with heavy rainfall predicted to last until nightfall.
A severe weather warning is current for the Illawarra region south of Sydney due to the risk of flash flooding.
The Bureau of Meteorology has warned the hardest hit areas are likely to be Wollongong, Bulli, Port Kembla, Albion Park, Kiama and Huskisson.
Six-hourly rainfall totals up to 140mm are possible, the bureau says.
A strong wind warning has also been issued for the the Illawarra on Sunday, while those along the Byron Coast, Coffs Coast, Macquarie Coast, Hunter Coast and Sydney Coast have been put on alert for Monday.
The NSW State Emergency Service has told residents and holiday makers in the Illawarra to stay indoors avoid unnecessary travel.
“Park your car under secure cover and away from trees, powerlines and drains,” the service said in an alert.
“If safe to do so, secure or put away items, such as outdoor furniture, trampolines and roofing iron that could blow around in strong winds.”