’Tis the season for big surf.

The National Weather Service predicts that a new northwest swell arriving this weekend should serve big-wave riders well, bringing even larger surf to ride into the new year.

“From our point of view, the big surf season has finally really kicked in,” city Ocean Safety Division Operations Chief Jim Howe said today. “We anticipate seeing surf above the 15-foot-face range for the next three to four weeks and going above that on occasion.”

A deep low-pressure system with storm-force winds off Japan’s northeast coast will generate a northwest swell in Hawaii, possibly larger than the current one, and is expected to arrive in the islands Saturday night and peak Sunday, holding through New Year’s Day.

“We are expecting heights coming in this weekend at 25-feet-plus,” said Leigh Anne Eaton of the National Weather Service, adding that there is also “a chance of a coinciding high tide and coastal wash.”

The northwest swell that brought 20- to 25-foot-face waves today, peaking tonight and coinciding with a high tide, will diminish by Friday.

But the high-surf warning was extended to 6 p.m. Friday for north shores of all islands except Lanai and Hawaii island, and west shores of Niihau and Kauai. A high-surf advisory for Oahu and Molokai’s west shores will also be in effect, with waves of 14 to 18 feet expected.

Two separate events, a large storm southeast of Kamchatka in the Russian Far East and a low-pressure system formed east of Tokyo on Christmas Eve, generated the current swell.

Oahu lifeguards were busy today, rescuing five people and issuing 700 preventive warnings to beachgoers at North Shore beaches, officials said. Waimea Bay had the most preventive actions, with 200 warnings issued.