The Hawkesbury River peaked at the major level late on Saturday evening, and at the moderate level at Windsor on Sunday.
As water levels began to recede, about 800 people in the Sydney region were still impacted by evacuation warnings.
NSW State Emergency Service assistant commissioner Dean Storey said it was likely these evacuation warnings would be in place over the next few days.
"It is our priority to get people back to their homes as soon as it is safe to do so," he said.
"Once the flood water recedes our crews will be out in force on the ground assisting with damage assessments."
So far dozens of properties in the NSW Illawarra region have been deemed damaged or uninhabitable. (Dean Lewins/AAP PHOTOS)
So far in the Illawarra region 57 properties have been found to be damaged, 28 inundated with flood water and 14 deemed non-habitable.
The Bureau of Meteorology said the worst of the weather has passed, with no thunderstorms forecast for Monday.
Residents have been warned the impacts of the weekend's record-breaking rain could still present danger in the region, with damage to roads and train lines.
The Hawkesbury River was expected to remain above the moderate flood level at North Richmond until Monday morning, and at Windsor until Monday afternoon.
The rain may have stopped but damage to roads still poses a hazard, residents have been warned. (Dean Lewins/AAP PHOTOS)
Parts of the South Coast train line have been closed due to damage from the weekend's flooding.
"The safety of our people and passengers is always our first priority and our engineers and work crews are mobilised across the rail network to assess and repair the damage," Sydney Trains chief executive Matt Longland said.
Some communities are also impacted by road closures, with Bells Line of Rd and Megalong Rd in the Blue Mountains among those shut due to flooding and damage.
The State Emergency Service had fielded about 4900 calls for help since the floods began as of Sunday evening.
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