A deep low pressure system crossing the southern Tasman Sea during Friday will bring a large swell to the NSW coast over the next few days.

Southern and central parts of the coast can expect a steady increase in swell during Friday afternoon and evening, creating hazardous surf conditions.

On Saturday, the hazardous conditions will extend to the northern coast, the Bureau of Meteorology said.

The dominant swell during this event will be from the south.

The significant wave height associated with this swell is expected to reach 3-4 metres, with a peak period of 13-14 seconds.

The maximum wave height will be considerably higher. This combination of wave height and period will result in very powerful surf.

Surf Life Saving NSW and Marine Rescue NSW advises that people in areas affected by hazardous surf warnings should consider staying out of the water, and avoid walking near surf-exposed areas.

In the wake of a number of rock fishing fatalities this year, 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.

Those boaters who do choose to go out should carry the appropriate safety equipment and wear a lifejacket.

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