Residents in low-lying areas around Manly Dam on Sydney's Northern Beaches have been warned to prepare to evacuate.
The SES warned that Manly Dam has reached amber alert.
Premier Dominic Perrottet said more warnings are expected to be issued.
LIVE UPDATES: Bodies pulled from Sydney floodwaters; NSW braces for more rain
"As we have been saying during this period of time and we will continue to repeat that message, if there is an evacuation warning in place, please get ready to leave," Mr Perrottet said.
"If there is an evacuation order in place, please evacuate, please follow the instructions of our state emergency services."
An emergency warning has already been issued, so those people in the affected area have been told if they will need to evacuate.
A previous alert announcing an evacuation has been removed after water levels in the dam dropped.
READ MORE: More than 60,000 people under evacuation warnings amid wild NSW weather
The Northern Beaches area is the latest to be inundated with the relentless rain hammering much of New South Wales.
Floodwaters are also quickly rising in Freshwater, Brookvale, Curl Curl and the surrounding suburbs.
A car park in Brookvale has about two feet of water in the bottom of it, and the water is up to the rim of wheels of vehicles on the nearby streets.
Pittwater Road in Manly has been inundated, and cars are beginning to float on the Roseville Bridge.
Roads are underwater in Manly Vale and some roads down into Freshwater and Curl Curl have been cut off.
Buses through the Northern Beaches and Lower North Shore are ending their trips due to the flooding.
