Residents of NSW have been urged to remain vigilant of potential flooding, despite this week's torrential rainfall beginning to ease.

Earlier this week, rainfall soaked Sydney and parts of the state, with some parts in Wollongong receiving more than 200 millimetres of rain in one night.

Speaking at a press conference today, NSW SES Acting Commissioner Deb Platz said, since Tuesday afternoon, 850 incidents across Sydney and the Illawarra coast had been responded to by volunteers.

The SES currently has more than 30 warnings in place, with 12 being emergency orders.

But Ms Platz said since, the weather has been contracting and that today most of the state "will only see limited amounts of rainfall".

"But that does not mean that the risk is not there.

"Because what we are going to see now is riverine flooding in many areas, particularly in the west of Sydney."

She said this riverine flooding would "continue predominantly throughout today and hopefully will ease later this afternoon and into tomorrow".

"So despite the fact that there are blue skies, we really need people to actually understand where they are going, what routes are actually open, and when they see flooded waters that you do not drive in those waters."

Rising floodwater prompted the closure of Richmond bridge on Friday afternoon — it remains inaccessible today.  

Windsor bridge remains open.

Ms Platz said all flood warnings are either minor or moderate, impacting the Hawkesbury Nepean rivers, the Cooks River, the Woronora River, Shoalhaven River, St George's basin and Hastings River.

Dam levels receding

Water NSW CEO Andrew George said that Warragamba Dam, located in Sydney's south-west, had peaked overnight.