(BIVN) – A High Surf Advisory has been issued for north-facing shores of the Big Island, to be in effect until 6 a.m. Tuesday. (UPDATE: The Advisory has been extended to 6 p.m. Tuesday)

The National Weather Service says “a large north-northwest (340 degrees) swell will bring dangerously high surf” to exposed shores. Surf heights of 12 to 16 feet are possible.

The Hawaiʻi County Civil Defense in a radio message urged beach-goers, swimmers, and surfers to “exercise caution and heed all advice given by ocean safety officials.”

A High Surf Warning is in effect for the other Hawaiian islands. The highest waves, 18 to 22 feet, were expected across north facing shores of Maui and Molokai.

The swell will gradually diminish and turn more northerly on Tuesday, forecasters say.