SEVERE weather generated by ex-tropical cyclone Uesi could impact the Hunter and Central Coast as early as this afternoon.
Any rain it brings could potentially impact flood-affected communities around Lake Macquarie and Tuggerah Lakes.
The Bureau of Meteorology has issued a Hazardous Surf Warning for the NSW coast for Friday and across the weekend as Uesi dissipates and becomes a tropical low and moves south off the state's east coast.
Swells of 3 metres to 4 metres are expected to pound the coastline.
Conditions across the Hunter and on the Central Coast are expected to be dangerous for coastal activities such as rock fishing, boating, surfing and swimming.
Surf Life Saving NSW said 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.
Director of lifesaving at Surf Life Saving NSW, Joel Wiseman, said surf conditions on the NSW coastline today and across the weekend would be large and dangerous.
"With conditions forecast to be hazardous today and across the weekend, we are urging members of the public not to engage in risky coastal activities," Mr Wiseman said.
"If people don't heed emergency service warnings and put themselves in danger in these extreme conditions, it's possible that lifesavers will not be able to save them."
A low-pressure inland trough is also likely to bring thunderstorms and flooding to the coast.
Director of Operations for Marine Rescue NSW, Andrew Crib, warned boaters, fishermen and surfers to avoid the ocean in coming days.
"The sea is a very dangerous place to be this weekend," he said.
Mr Crib also warned anyone planning to travel through or across flood waters or inland rivers, particularly those in fire-affected communities, to be vigilant and rethink the need to do so.
"If you have to go out, there's a lot of submerged debris out there," he said.
In Lake Macquarie, erosion at the southern end of Blacksmiths Beach is expected to worsen in coming days.
The beach has been closed to 4WD vehicles until further notice.