One southbound lane on the Federal Highway has reopened after it had been closed due to flooding.
One lane remained closed between the Hume Highway and Canberra, as of 8am.
Motorists should reduce speed and drive to the conditions.
Northbound traffic has not been affected.
A deluge of rain hit the Canberra region and NSW South Coast over the weekend, with more 200mm falling in some areas over the 24 hours to Sunday, which led to widespread flooding and rising rivers.
Residents of Moruya, Sussex Inlet, Terara, East and North Nowra and Worrigee were told to evacuate to higher ground on Sunday night.
Rainfall had begun to ease on Monday morning but the Bureau of Meteorology expected the Shoalhaven River at Nowra would peak at 4.4 metres by 1pm.
A flood warning for the Molonglo River at Oaks Estate, Queanbeyan was cancelled early Monday as it dropped below flood levels just after 5am.