The dangerous surf warning is in place for NSW from the South Coast through to Northern NSW with the conditions expected to build up overnight on Thursday.

Swells are predicted to peak at around 3-4 metres in some areas, but are forecast to be larger and stronger offshore.

Southern facing beaches will encounter the strongest of the conditions as the southerly swell travels up the coast.

At this stage Southern NSW will experience this swell from Thursday evening and it is expected to continue into Friday before easing on Saturday morning.

Surf Lifesaving NSW operations manager Andy Kent urged the public to take the warnings seriously.

“The best advice we can give people is to be aware of their environment and the changing conditions. Take the time to study a recent weather forecast before heading out and let others know what your plans are,” he said.

“We know the weather isn’t the best for the next few days with strong winds and rain forecast so people may choose to stay inside.

“However, in saying that we encourage everyone to take their safety seriously regardless of the type of activity they are doing.”

Mr Kent also advised all beachgoers and rock fishers not to take any unnecessary risks and that volunteer surf lifesavers will be on patrol duties each weekend until the season concludes on Tuesday, April 25.