The National Weather Service has issued a high surf warning for the north and west-facing shores of Niihau, Kauai, Oahu, and Molokai and the north-facing shores of Maui.
A high surf advisory is also in effect for the west-facing shores of Maui.
Forecasters say a powerful northwest swell will build through Thursday night and peak by Friday, producing hazardous surf along exposed north and west shores.
Surf is expected between 20 and 25 feet along the north and west-facing shores of Kauai and Niihau, and along the north-facing shores of Oahu, Molokai, and Maui.
Surf along the west-facing shores of Oahu and Molokai is expected between 15 and 20 feet.
Expect ocean water occasionally sweeping across portions of beaches. Expect very strong breaking waves and strong longshore and rip currents.
Anyone entering the water could face significant injury or death.
Boaters should be aware of an increased number of surfers and body boarders utilizing the harbor channel to access surfing areas.
The high surf warning will remain in effect until 6 a.m. Saturday.