Evacuations have been ordered in southern Sydney as flood warnings continue after days of heavy rain.

Residents in Camden, Menangle and around the Milperra Bridge at Chipping Norton were told to prepare to evacuate on Friday, while there were multiple flood warnings for southern Sydney suburbs and Goulburn.

Also on Friday, Sydney’s largest dam was spilling after some parts of NSW received nearly double their monthly average rainfall in the days since Wednesday.

While the rain was starting to ease across much of Sydney on Friday, flood risks remained with the deluge hitting saturated catchments and pushing several other dams beyond capacity.

The flood threat was also heightened further south of Sydney with the surface trough that has generated the heavy falls moving south on Friday.

Warragamba dam began spilling on Friday morning at a rate of about 150 gigalitres of water a day. Inflows were at 270GL a day and rising, WaterNSW said.

It is the third consecutive month the dam has spilled.

Friday’s update came after the catchment received 87 millimetres of rain in 48 hours.

NSW SES acting commissioner Dallas Burns said the focus had shifted to the Hawkesbury-Nepean, with flooding expected at North Richmond later on Friday.

Premier Chris Minns said resources had been moved into the catchment bordering Sydney’s west.

“We’re expecting potentially flash flooding … but riverine flooding may be an issue over the weekend,” he said on Friday.

Dams south-west of Sydney at Woronora, Nepean, Cataract, Cordeaux, Avon and Tallowa were all spilling on Friday morning as well, along with storage areas in the Blue Mountains.

A severe weather warning issued by the Bureau of Meteorology advised more heavy on the south coast of NSW on Friday afternoon, as rain eased around Sydney.

As much as 100 millimetres could fall in six hours in some areas, while others have already copped a drenching, the bureau warned.

“For the second half of the day today, the focal point of rain will become the south coast,” senior forecaster Angus Hines said.

“Those spots around the Illawarra and Sydney might see a further shower this afternoon but the intensity and persistence of the rain should dial right back.”

At Cringila in Wollongong’s south, 214 millimetres of rain fell in 24 hours to 9am on Friday, with 204 millimetres at Port Kembla and 156 millimetres at Wollongong.

Flood risks remain as the downpours ease.

“Any further wet weather in the next few hours and for the rest of the day, will be falling onto saturated land … adding to or extending potential flooding impacts,” Hines said.

The Nepean River may reach 10 metres by noon at Menangle, south-west of Sydney and downstream from Warragamba. The NSW State Emergency Service has advised people there to monitor conditions and alerts.

Moderate flooding is likely along the Colo, Hawkesbury and Nepean rivers in Sydney’s west and the Georges and Woronora rivers in the city’s south.

“The rivers have seen a rapid response to the amount of rainfall in the past 24 to 36 hours,” Hines said.

“As this rain that’s fallen over the last day or two works its way down through the river network, there are other waterways and rivers that could rise and exceed their flood thresholds.”

The SES conducted 49 flood rescues, responding to 447 incidents across the state in the 24 hours to 5am on Friday. The majority were in the south-eastern region hit by the heaviest rain, with 291.

Buses have replaced trains between Wollongong and Port Kembla due to flooding.

-with AAP