A high surf advisory has been extended until 6 p.m. today for the north and west shores of Oahu, Kauai, Niihau, and Molokai and the north shores of Maui.

The National Weather Service said surf along the north shores will be 14 to 20 feet; surf along west shores will be 10 to 14 feet.

Strong currents will make swimming “difficult and dangerous,” forecasters said.

On Sunday, Waianae Ocean Safety lifeguards had just completed a regular shift when they went to the aide of a surfer who was in trouble at Keaau Beach.

The surfer got in trouble in 8 to 12-foot waves at 5:40 p.m.

Lifeguards responded, rescuing the surfer and bringing him to shore safely. He did not require medical treatment.

Lifeguards are normally on duty from 9 a.m. to 5:30 p.m.

Meanwhile, a small craft advisory is in effect for Hawaiian coastal waters until 6 a.m. Tuesday.

The weather service said mariners can expect winds of about 25 mph and seas of 8 to 11 feet, the result of strengthening tradewinds and a moderate northwest swell.

The tradewinds will blow through much of the week with high pressure north of the islands. Clouds and showers will favor windward and mauka areas, but the trades could drive a few showers into leeward areas, the weather service said.