A high surf warning that covers most islands has been extended until 6 a.m. Saturday, the National Weather Service said.

The warning, which was set to expire at 6 p.m. Friday, covers north and west shores of Niihau, Kauai, Oahu, Molokai and Hawaii island, and the north shores of Maui.

Forecasters said waves of 22 to 26 feet are hitting north shores, while west shores are seeing surf of 15 to 20 feet. The waves will gradually diminish through the night and fall to advisory levels Saturday morning, the weather service said.

“Expect ocean water surging and sweeping across beaches creating the potential for impacts to coastal properties and infrastructure, including roadways,” the warning says. “Powerful longshore and rip currents will be present at most beaches. Large breaking waves and strong currents may impact north- or west-facing harbor entrances and channels causing challenging boat handling.”

The weather service in Honolulu also has issued a high wind warning for Hawaii island summits until 6 p.m. Saturday, with sustained winds of 40 to 65 mph and gusts over 75 mph possible for Mauna Loa and Mauna Kea.

Forecasters said a “robust subtropical jetstream will bring dangerously strong west winds to the Big Island summits through Saturday. Winds are expected to begin to decrease Saturday, with advisory level winds possible Saturday night and Sunday.”