A high surf advisory has been issued for the north and west shores of the Hawaiian Islands from Niihau to Maui, in effect until 6 a.m. Thursday.

The National Weather said a “dangerous, long-period northwest swell” is expected to travel down the isle chain today and tonight, and to hold through Thursday.

Surf of 18 to 23 feet is expected along north and west shores of Niihau and Kauai, while surf of 15 to 20 feet is expected along the north shores of Oahu, Molokai and Maui. Surf of 10 to 15 feet is expected along west shores of Oahu and Molokai.

Officials warn of shore break, strong, breaking waves and rip currents, making swimming difficult and dangerous.

Beachgoers, swimmers and surfers should heed all advice given by ocean safety officials. Boaters should also watch out for recreational surfers and body boarders utilizing harbor channels to access surfing areas.

Today’s forecast is mostly sunny with isolated afternoon showers, highs from 79 to 84 degrees Fahrenheit and variable winds up to 15 miles per hour. Lows tonight range from 63 to 68 degrees.

Weather patterns should remain stable and dry through Thursday, forecasters said, with light and variable winds for the western half of the state. Light, windward showers are expected for East Maui and Hawaii island.

A cold front, however, is expected to stall near Kauai, bringing wet and unsettled weather across the western end of the state late Thursday and Friday, and possibly last through Saturday. Trades are expected to return for the weekend.