Heavy rain that has lashed parts of NSW over the past 48 hours has put rivers in Sydney's north and west at risk of flooding.
The Bureau of Meteorology (BOM) said there was at least a 70 percent chance of minor flooding on the Nepean and Hawkesbury rivers on Friday morning.
The BOM will issue flood warnings if the rain gets heavier, with experts watching flood gauges at Wallacia and Penrith, in the city's west and at North Richmond, Windsor, Sackville and Lower Portland, to the north.
The State Emergency Service (SES) urged people living or working along the two rivers to monitor the weather and be prepared to move to higher ground.
"Flooding will initially affect low-lying farmland and local roads near the rivers and their tributaries," the SES said.
"Farmers should watch the weather and be ready to move pumps, other equipment and livestock away from rising waters.
"Travellers should avoid driving through flood waters, which could be deeper or faster-flowing than they look."
More heavy rain along NSW's coast on Wednesday caused flash flooding in Sydney and the Central Coast.
It caused delays on the roads and about 1300 homes in the Sydney suburbs of Five Dock, Hornsby and Somersby were without power for much of the afternoon.
The outlook is gloomy for Thursday, with more rain forecast across the state.
