Severe wet weather is spreading across the NSW South Coast and Illawarra, cutting roads and making trips by cars perilous in some locations.

Parts of the Shoalhaven experienced more than 150 millimetres of rain, with Vincentia in Jervis Bay receiving 177mm in the 24 hours since 9am Wednesday.

Greenwell Point received 159 millimetres, and Shoalhaven Road in Nowra receiving 123mm.

SES South East Deputy Zone Commander Barry Griffiths said they had already carried out two flood rescues.

"So far we have had 30 incidents we have responded to," he said.

"Two of those have been flood rescues in and around Nowra and we will continue to get flood-related, storm-related calls for assistance this morning. 

Angus Hines from the Bureau of Meteorology said the rain will continue to fall throughout the day as it gets pushed from the ocean over the land and heads north.

"A little further north it's dry for now, but it's not really looking to stay that way today," he said.

"It covers pretty much all of the Illawarra at the moment, it goes down into the northern part of the south coast forecast district area, and it pushes up into the Central and Southern Tablelands area as well," he said.

Some areas are expected to receive 24-hour totals of up to 250 millimetres while parts of Sydney are also expected to experience heavy falls.

Allan Harvey runs Greendale Cafe at Greenwell Point east of Nowra and had to close on Thursday. 

"We usually arrive at work at 7am and when I turned up this morning I could hardly get into the car park," he said.

"We are flooded at the front so it's almost impossible to get into the building and it's a historically listed site where we are, so a lot of the buildings are not lifted up off the ground.

"So businesses are really suffering in our area."

After lunch another flood rescue occurred at Huskisson following earlier rescues at Berry and Nowra.

The SES issued a flood Watch and Act for residents in Sanctuary Point to prepare to evacuate as Tomerong Creek rises.