Flooding on Sydney coast forecast to hit on Monday

An east coast low bearing down on Sydney overnight is expected to cause more heavy rainfall on an already saturated catchment, leading to major floods on the Hawkesbury, Nepean and Colo rivers.

Andrew Edmunds, a spokesman for the New South Wales State Emergency Service NSW SES Floods, said conditions are likely to worsen before they get better, and that they are likely to exceed the flood levels reached in the three recent major Hawkesbury flood events since March 2021.

There is a burst of heavy rainfall overnight that is expected to cause the expected flood peaks.

As the low approaches, we're seeing increasing rain late tonight, early into tomorrow morning, according to forecaster Jonathan How from the Bureau of Meteorology.

We are warning of the potential for six-hourly rainfall totals of up to 120 millimetres. Heavy falls may also hit parts of the Illawarra, inland from Wollongong, which have already seen more than 600 mm of rain since Friday.

That is almost half of Sydney's average annual rainfall in just two days.

Damaging winds and surf on the way are on the way.

The Bureau of Meteorology said that flooding is not the only hazard the Sydney region is facing.

We're going to see some damaging winds tonight, Mr How said.

We're already seeing strong winds developing along the Sydney coasts of around 70 to 80 kilometres an hour.

As the low pressure system moves toward the coast, we'll see a ramping up of the winds tonight. A damaging surf warning is in place, with waves around five metres coinciding with high tides tonight, leading to beach erosion.

The rain is expected to be a little bit less on Tuesday, but the floodwaters may remain high.

It's unfortunate that it's happening again, Mr How said.

The overnight downpour resulted in Sydney's main dam, Warragamba, spilling hours earlier than predicted, according to Tony Webber, a spokesman for dam operator WaterNSW.

The storage has reached capacity and exceeded capacity at 2 am this morning, well ahead of expectations due to the intensity of the rain in the catchment, he said.

According to WaterNSW, water was flowing from the dam at a faster rate than at the peak of the major floods of 2021, according to the dam's water.

Mr How said saturated soils were compounding the intense rain, accelerating the rate of river rise.

The Hawkesbury River in North Richmond was forecast to reach around 15 metres late Sunday night, with major flooding.

The Bureau of Meteorology says further rises are possible with the forecast rainfall.

Andrew Edmunds of NSW SES said 41 evacuation orders and 44 warnings have been issued to communities in the Hawkesbury-Nepean, Western Sydney and Illawarra areas.

The SES advises those who are subject to flood warnings to be prepared to leave.

Have a emergency kit ready for you with warm clothes, important documents, medications, laptops, phones, and chargers, he said.

You should try and keep up to date overnight on the SES website and Facebook pages and the Bureau of Meteorology website.