Evacuation and extreme weather warnings issued after heavy rain ...

• In short: Heavy rain has fallen across Sydney and Wollongong and caused flash flooding overnight.
• The torrential falls are part of a broader rain event that soaking eastern Australia as it contracts south.
• The Bureau of Meteorology says dangerous thunderstorms are likely to produce intense rainfall that may lead to dangerous and life-threatening flash flooding across Sydney, Parramatta, Wollongong, Bowral, Campbelltown and Port Kembla.

A deluge overnight has dumped heavy rain across parts of Sydney and the Illawarra, prompting emergency evacuation warnings and rapid river rises.

The torrential falls are part of a broader rain event soaking eastern Australia, and has triggered more than 50 flood watches and warnings from southern Queensland to the NSW south coast.

Bellambi Point, north of Wollongong, has received 190 millimetres of rains since 9am yesterday — with 35mm falling in the half hour to 6:10am.

Where to find emergency assistance and information:

• For emergency assistance contact SES in NSW 
• If your life is at risk, call Triple-0 (000) immediately
• For the latest weather updates visit the Bureau of Meteorology in NSW here
• ABC Emergency contains planning and advice, and incident map and more
• If you're not sure what to do when there's a flood, here's the best way to plan
• Tune into your local ABC Radio Station

In Greater Sydney, the biggest falls have been experienced in Penrith, where 167 millimetres was recorded, and Terrey Hills and Canterbury, which have received more than 150mm since 9am yesterday, with the biggest falls coming overnight.

Gosford in the Central Coast has been soaked with 161mm.

Multiple rainfall records have been broken by the deluge, including:

• Penrith — 167mm — heaviest rainfall on record (weather station opened in 1995)

• Bellambi — 195mm — heaviest rain in six years.

• Chatswood — 189mm — heaviest in four years. Chatswood was also the wettest Sydney suburb.

After bringing falls in excess of 100mm to southern Queensland and the NSW Northern Rivers on Thursday, the heaviest falls drifted south on Friday morning to the Mid North Coast.

Taree and Port Macquarie were both drenched by more than 100mm by the evening — about a months' worth of rain — with those totals now about 130mm since 9am Friday.

The rainfall and inflows from days of wet weather to the Hawkesbury River overnight have prompted several low-lying communities to be told to prepare for evacuation.

The Bureau of Meteorology (BOM) has issued a string of flood and extreme weather alerts.

There was a warning very dangerous thunderstorms were likely to produce intense rainfall that may lead to dangerous and life-threatening flash flooding throughout Saturday morning across Sydney, Parramatta, Wollongong, Bowral, Campbelltown and Port Kembla.

Warragamba Dam has reached full capacity and began spilling at 5:45am, Water NSW said.

Highways closed by floodwaters

Some major roads in Sydney and the Illawarra have been closed due to flooding.

In Sydney’s south, the Princes Highway is closed northbound at Engadine, and Bexley Road is closed in both directions at Bexley North. 

The Illawarra Highway is closed in both directions between Tongarra Road and the M1 at Albion Park, and also at Macquarie Pass. 

Motorists have been advised to avoid non-essential travel and not to drive through floodwaters. 

A woman had died following a head on collision in wet conditions in the NSW Central West on Friday afternoon.

Emergency services were called to the Castlereagh Highway south of Mudgee just after 2pm following the crash between a ute and an SUV.

A 32-year-old woman was taken to the Mudgee hospital in a critical condition but died a short time later.

Five other people were taken to hospitals across the state following the crash including two young girls aged two and six.

Damaging easterly winds averaging gusts up to 70 kilometres per hour and peak gusts of about 90kph are possible in the South

West Slopes including coastal parts of the Sydney metropolitan area.

Winds of up to 125kph are likely for alpine areas, the BOM said.

Residents on alert as Hawkesbury River rises 

New South Wales State Emergency Service has issued several warnings and evacuation alerts for river systems of the Western Sydney and Illawarra regions.

After consistent, heavy rain overnight, the BOM said the Hawkesbury River at Windsor was likely to exceed the moderate flood level of 7 metres this morning.

An evacuation order is in place for residents in the Gronos Point area north of Windsor.

People living in low-lying farmland at Agnes Banks, south of Richmond, have been ordered by the SES to evacuate by 7am, along with residents of the Riverside Caravan Park in Cattai.

An evacuation centre has been set up at Richmond Club.

Residents at Cornwallis and the eastern part of Richmond Lowlands, and parts of Lower Portland on the eastern side of the Hawkesbury River, have been told to evacuate by 8am.

There is also a watch and act alert for low-lying areas of the Colo River.

Major flooding of up to 12 metres is also likely early this morning at the Upper Nepean River, and is expected to reach minor levels at Menangle Bridge, Camden and Wallacia Weirs.

SES on alert for 'volatile' conditions

NSW SES spokesperson Andrew Edmunds said preparations were in place to respond to the intense wet weather affecting the Hawkesbury and Nepean region.

"We're expecting significant rises on the Hawkesbury, Nepean today and have flood rescues teams, aviation assets and high-clearance vehicles pre-positioned and ready to respond to any incidents," he said.

"We're expecting a numbers of road closures as a result of flood water and also some key bridges to close due to floodwaters."

Evacuation centres have been set up in parts of Greater Sydney including Bankstown, Liverpool and Richmond.

Mr Edmunds cautioned the state's residents to make responsible decisions and follow the advice of emergency services.

The rain across Sydney slowly increased through Friday and by sunset Observatory Hill had already collected more than 160mm for the event, the wettest 48 hours in four years, although even heavier rain arrived overnight.

The band of torrential falls is heading south down the coast and should clear from Sydney by mid-morning, before contracting to the South Coast by the afternoon where it should ease by tonight.

The deep trough responsible for the deluge has also strengthened winds and whipped up huge waves, already peaking up to 7 metres off the coast of Sydney on Friday evening.

While showers and storms will continue for parts of the state on Sunday, no further widespread heavy rain is likely.