A high surf advisory has been issued for the north and west shores of most Hawaiian islands, effective until 6 p.m. Saturday.

Additionally, a high surf advisory for the west shores of Hawaii island has been extended until 6 p.m. Saturday.

National Weather Service forecasters say a large, west-northwest swell is expected to peak tonight.

Surf is expected to reach 15 to 20 feet along the north shores of Niihau, Kauai, Oahu, Molokai, and Maui, and 8 to 12 feet along west shores. Waves are expected to reach 7 to 10 feet along the west shores of Hawaii island.

Officials say the swell is expected to slowly decrease Saturday, but another west-northwest swell is due to arrive on Monday.

Weather officials warn of strong currents and breaking waves, which will make swimming dangerous.

“Heed all advice from ocean safety officials,” forecasters said. “When in doubt, don’t go out.”