Most of the Hawaiian Islands experienced high surf Thursday as a strong low-pressure system to the northeast generated a large north swell.

While a high-surf warning for the north and west shores was set to expire at 6 a.m. today, surf will remain at advisory levels throughout the day, the National Weather Service said.

Until then, surf of 25 to 30 feet was battering the north shores, with occasional sets of 35 feet on the outer reefs, the agency said. That will drop to 20 to 25 feet Friday.

East shores can expect surf of 10 to 15 feet.

As of 4 p.m. Thursday, Oahu lifeguards conducted two rescues and 2,020 preventive actions on the North Shore, and 12 rescues and 1,420 preventive actions on the east shores, according to Emergency Services Department spokeswoman Shayne Enright.

The waves will gradually decline today.

Meanwhile, a small-craft advisory remains in effect for Hawaii waters until 6 p.m. Sunday, with strong winds in the channels and seas of 12 to 17 feet today. That will drop to 6 to 12 feet Saturday, the weather service said.

Strong and gusty northeast winds will continue across the state through tonight, and possibly through the weekend. Lanai, as well as the leeward Kohala and Kohala mountain areas on the Big Island, will have the strongest winds, with gusts possibly reaching 50 mph, forecasters said.