Update 6.45am: According to Live Traffic, flooding is continuing to affect traffic on the M1 Princes Motorway southbound near the Northcliffe Drive off-ramp at Berkeley.
One of two southbound lanes remains closed.
RMS are attending, while motorists are advised to reduce speed and exercise caution.
A driver has been removed from a car that became stuck in floodwater at Albion Park on Sunday afternoon.
NSW State Emergency Service (SES) flood rescue operators were called to a section of Taylor Road just before 4.30pm, following reports of a vehicle stranded in the water.
Shellharbour SES deputy commander Ray Merz said it appeared the driver, a young man on a pizza delivery, "decided to risk it a little bit more than he should and he's now not going to finish his pizza route".
"He's driven into the water and then realised it was quite a bit deeper than he thought it was and the car certainly wasn't equipped for it," Mr Merz said.
The water was about 60 centimetres deep.
SES volunteers retrieved the green P-plater from the driver's seat.
"He was just sitting there. I think he was more embarrassed than anything else," he said.
Mr Merz said Taylor Road was the unit's "biggest flash flood hotspot".
"You get a lot of short, intense bursts of rain and it regularly goes underwater," he said.
"But just as quickly as it goes up, when the rain stops it goes down.
"Unfortunately he decided to take it on at the wrong time."
Mr Merz said there had been a number of intense and prolonged heavy bursts of rain on Sunday and the Taylor Road incident was an example of what not to do.
"Don't drive into floodwater ... just stay out of it," he said.
At this stage, the Illawarra Highway between Albion Park and the Princes Highway/Motorway roundabout at Albion Park Rail remains open.
However, flooding is affecting traffic on the M1 Princes Motorway southbound near the Northcliffe Drive off-ramp.
According to the Bureau of Meteorology, Albion Park received 30mm of rain between 9am and 5.30pm on Sunday.
Half of that total fell in the 60 minutes from 3.30pm.
Elsewhere, 24.2mm has been recorded at Bellambi since 9am, while the weather station at Kiama has registered 25.2mm.
Falls on Sunday have been heaviest further south, with 38.8mm at Nowra and 52.4mm at Jervis Bay Airfield between 9am and 4.30pm.
The bureau said a high pressure system over the southern Tasman Sea is directing humid winds into two troughs, one near the NSW coast and the other over the state's west, leading to showers and thunderstorms in many eastern districts.
"Within the coastal trough, a low pressure circulation is expected to intensify overnight, bringing heavy rain to parts of the southern coast, before weakening and shifting northwards later Monday," the bureau said.
"Little change is expected through the remainder of the week, as the coastal trough looks set to remain the dominant feature, maintaining showery conditions in the east."
We're continuing to see heavy falls about central parts of #NSW coast. Yesterday #Sydney & many #CentralCoast locations saw around 30-50mm, while higher totals include Wyoming 134mm & #Gosford 124mm. Tomorrow the heavy rain will shift more south along the coast. #sydneyrainpic.twitter.com/FjxuEmhuWf— Bureau of Meteorology, New South Wales (@BOM_NSW) March 17, 2019
Mr Merz said the "night's not over yet", with the SES crews told up to 100mm of rain could fall during Sunday afternoon and evening.
Up to 20mm is forecast in Wollongong on Monday, according to the bureau, with the possibility of a storm during the afternoon and evening.
A further 10mm could fall on Tuesday, and up to 5mm on Wednesday, before showers begin to ease.