The Bureau of Meteorology has issued a hazardous surf warning and marine wind warning for the NSW coastline through to at least Sunday, May 24.
Conditions are expected to be hazardous for coastal activities such as rock fishing, boating, surfing and swimming.
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.
Andrew Ugarte, NSW State Operations Manager at Surf Life Saving NSW, said that conditions on parts of the NSW coastline are already very dangerous.
"We urge members of the public to exercise extreme caution on the NSW coastline today and across the weekend and not to engage in risky coastal activities," Andrew Ugarte said.
"If people put themselves in danger in these extreme conditions, there's a real chance that lifesavers will not be able to save them, or at the very least, risk their own lives in doing so."
With swells up to four metres forecast in some locations and gale-force winds, there is a threat of coastal inundation, erosion and flooding in low-lying areas.
Surf Life Saving NSW will have duty officers and surf rescue assets on standby across the weekend.
The Surf Rescue 30 Offshore Rescue Boat based in Sydney, Surf Rescue 40 and Surf Rescue 50 jetboats and crews will also be on standby in Ballina and Kiama to respond to any critical coastal incidents.
Supporting the offshore rescue boats will be RWC (jetski) operations and the SLSNSW State Operations Centre will be fully operational. Surf Rescue emergency call-out teams will remain on high alert across the weekend.
The high winds and large surf conditions mean most beaches and rock platforms in particular will be treacherous this weekend.
"The forecast weather pattern will produce high winds, damaging surf with significant wave height and substantial rainfall in some areas. It will create extremely dangerous conditions for swimmers, surfers, rock fishers and boaters," Mr Ugarte said.