An SES flood evacuation warning for low-lying parts of Goulburn remained in place on Tuesday night, after more than 120 millimetres of rain in 24 hours.
The NSW SES said evacuation remained possible for properties along the Wollondilly and Mulwaree rivers, with residents warned to await further instruction.
Residents at Towrang, north of Goulburn, were also warned that their homes could become isolated if low-level crossings were closed.
The ACT can expect partly cloudy conditions with isolated showers clearing later in the day.
Snowfall is possible above 1700 metres during the morning and winds are expected to be southeasterly to 25km/h.
Canberra's overnight temperature was expected to fall to 4 degrees with a daytime top of 14.
The warnings came as SES crews have doorknocked homes in Albion, Avoca and Derwent streets and in other low-lying areas.
Wet conditions also saw the Oaks Estate Crossing area closed due to flooding from 7pm.
Roads ACT is expected to review conditions in the area on Wednesday before deciding if it can be reopened.
The Kings Highway at Clyde Mountain was reopened after a second landslip in less than 24 hours.
Traffic was blocked from the area for about 1½ hours from 1.30pm, with a small amount of debris breaching a safety fence.
One lane of the highway was reopened to traffic at 5pm, with motorists passing through the site assisted by traffic control crews.
Intermittent closures of about 15 minutes are expected on Wednesday, with motorists encouraged to allow extra travel time.
RMS spokeswoman Marnie Procter told Fairfax Media it was possible the slip would extend the work timeline.
She said any closures needed would be carried out after the school holidays and RMS would advise the public of changes.
SES volunteers responded to more than 600 requests for assistance from residents including on the South Coast in the past few days.
A spokesman said local river flood levels near south coast communities were being monitored. The Bureau of Meteorology warned sheep graziers that low temperatures, showers and strong south-easterly winds were expected into Wednesday in the ACT forecast area as well as the Snowy Mountains.
A high risk of losses of lambs and sheep exposed to these conditions remains. The forecast for Thursday is for patchy fog and frost with a low of 1 degree and a top of 15.
Areas of fog and frost are expected on Friday with temperatures ranging from minus 1 to 15 degrees.