With Sydney drenched in winter sun, a trip to the beach might be tempting.

But the Bureau of Meteorology has issued a hazardous surf warning for the NSW coast, including advice from emergency services to stay away from the water.

A large southerly swell pounds South Curl Curl rock pool. Credit:James Brickwood

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

Bureau meteorologist Rob Taggart said a low pressure system over New Zealand was producing big swells and rough conditions that have crossed the Tasman.