Earlier: The South Coast is "on track" to encounter an east coast low that is expected to move south from northern NSW after thunderstorms and a drenching overnight, with extreme weather conditions set to take hold later on Saturday.

Bellambi Point received 96.4mm of rain in the 24 hours to 9am on Saturday – almost its entire June average of 113mm. The bulk of the rainfall, 95.6mm, fell since 10.30pm on Friday  

Albion Park was soaked with 56.4mm in the 24 hours to 9am Saturday, while 66.0mm fell at Kiama and 45.2mm was tipped out of the rain gauge at Nowra. 

Bega recieved 41.8mm, Merimbula 15.2mm, Moruya Airport 21mm, Moruya Heads 18mm, Narooma 20mm and Ulladulla 24.2mm.

Weekend rainfall totals of between 80 and 150 millimetres are expected as rain sets in, with isolated falls of 200 and 300 millimetres possible along the coast.

The Bureau of Meteorology (BOM) issued a severe weather warning on Saturday morning, forecasting the development of an east coast low as a low pressure system moves south from Queensland late on Saturday, bringing with it damaging winds, heavy rainfall and dangerous surf.

Abnormally high tides will contribute to very heavy surf on the NSW coast, with beaches along the state's coastline expected to close over the weekend.

Tristan Meyers, meteorologist at Fairfax Media's Weatherzone, said the coastal region will bear the brunt of the weather system when it reaches Sydney and the Illawarra on Sunday and that the city was "on track" to receive the extreme weather predicted by the BOM.

"There is more to come, the rain is going to intensify with less showers and more steady rain really picking up this afternoon and overnight," Mr Meyers said.

"We urge people to make sure to secure any loose items outside, make sure cars are parked in garages and not under trees and to keep up to date with the latest warnings.

"Beaches will be the worst places to be."

Winds are expected average at 60km/h and peak at 90km/h on the coast, he said.  

A wind gust of 72km/h was recorded at Kiama about 6.40am on Saturday, while a 63km/h gust was felt at Bellambi Point at 5.43am.

Willy Weather predicts wave heights of about 5.2m at North Wollongong beach, where swell is expected to peak about 4am on Sunday.

The Transport Management Centre reports that while roads are extremely wet and there are areas where water is affecting traffic, no major roads or highways are closed in Sydney or the Illawarra.

Just after 8am, Wollongong City Council said water was over the road on Pioneer Drive at Woonona, about 200 metres north of Bellambi Lane.

“Smaller vehicles recommended to use Memorial Dr or Princes Hwy instead,” the council tweeted.

In the Royal National Park, Audley Road at Audley Weir has been closed by water over the road.

Elsewhere, all Wollongong and Shellharbour council sportsgrounds have been closed due to the overnight deluge and forecast wet weather.

Wollongong Coast

- with smh.com.au