A weakening low pressure trough lies off the NSW coast and it is expected to bring king tides along the entire state's shoreline.

Abnormally high tides are possible on Tuesday morning's high tide along the Illawarra coast.

Water levels during the high tide may be near or exceed the highest tide of the year and cause inundation for low-lying coastal areas.

Read more: Clean up continues as roads remain closed around Illawarra

Surf and swell conditions are expected to be hazardous for coastal activities such as rock fishing, boating, and swimming the regions shoreline.

This follows days of heavy rain, damaging winds and dangerous surf over the weekend.

There are a number roads closed around the region.

Residents should never drive, walk or ride through floodwater.

People should consider staying out of the water and avoid walking near surf-exposed areas.

Rock fishers should avoid coastal rock platforms exposed to the ocean and seek a safe location that is sheltered from the surf.

Boaters planning to cross shallow water and ocean bars should consider changing or delaying their voyage.