The Hawkesbury River started flooding North Richmond in the early hours, with parts of Penrith also starting to flood with predictions of worsening conditions including for the town of Windsor.
South west of the city people in parts of Georges Hall, Chipping Norton, Lansvale, Milperra, Moorebank, Warwick Farm, as well as parts of Camden were ordered to leave by 3am.
Officials warned the areas were facing flooding similar to March 2021, when hundreds of homes were wrecked by floods.
But some areas around the Hawkesbury could be even worse hit this time.
NSW SES bosses admitted the situation was worse than expected.
“It is a very dire situation at the moment,” SES Commissioner Carlene York told A Current Affair.
“It’s more serious that what we had anticipated or what the forecast was.
“The Warragamba Dam has started to spill across the state, we’ve got 31 evacuation orders out [and] seven evacuation warnings.
“We’ve put out an order around the Redman Dam which is near the Hawkesbury River for those houses downstream, because there is a chance it may burst.”
North west areas told to leave include: parts of Agnes Banks, North Richmond, Cattai, Sackville, areas north of Bligh Park, Lower Portland, Freemon’s Reach, Gronos Point, Leetsvale and Ebenezer.
Picton and Menangle in Macarthur, and Narrabeen on the northern beaches are also on alert.
People on the NSW South Coast and Illawarra are also being told to prepare for possible flooding.
Up to 80 and 120 mm of rain within six hours is likely to fall, forecasters said- with up to 200mm possible in some spots.
Wind gusts of 90 km / hour are also predicted.
Flood clean-ups underway after devastating deluge
Meanwhile, further north, the town of Ballina remains underwater as waters in Lismore and Brisbane begin receding.