A large north-northeast swell is expected to bring surf up to 20 to 30 feet along the north shores of all islands and prompted an extension of a high surf warning for all islands.

The high surf warning is in effect for the north shores of all islands and is in effect through 6 p.m. Saturday.

A high surf advisory is in effect for the west shores of Hawaii island and is due to expire along with the warning.

The National Weather Service said a large medium-period swell will move into local waters today, bringing warning-level surf through Saturday. Tradewinds are expected to ease today, becoming light and variable Saturday.

“Expect very strong breaking waves and powerful currents,” the NWS said in a bulletin. “Waves breaking in channel entrances may make navigating the channels dangerous.”

Following the easing of gusty tradewinds, forecasters expect humidity and showers to increase after Sunday.

Oahu should see isolated windward showers, highs from 75 to 80 degrees and tradewinds of 15 to 25 mph for the rest of today, weather officials said. Temperatures are expected to dip into the 60s tonight.