A large northwest swell is expected to arrive later this evening, prompting a high surf warning for Kauai and Oahu, starting at 6 p.m.

The National Weather Service is expecting surf of 22 to 28 feet for north and west shores of Kauai, and 20 to 25 feet for north shores of Oahu.

Surf for the affected shores begins rising at 6 p.m. today, and the warning remains in effect until 6 a.m. Wednesday.

A passing cold front north of Hawaii, meanwhile, is expected to keep trades in the light to moderate range and in an east-to-southeasterly flow pattern through Wednesday, forecasters said. Isolated to scattered showers are expected mostly over mauka and interior areas for the smaller isles during afternoons and early evenings.

Today’s forecast is mostly sunny for the smaller isles, with brief passing afternoon showers for Kauai and Oahu, and highs from 80 to 85 degrees. Tonight is expected to partly cloudy with isolated showers and lows dipping to 63 to 68 degrees.

Despite the cooler nighttime temperatures, Kahului on Sunday recorded a record high of 88 on Sunday, surpassing the previous record of 87 for that day set in 1952.

Tradewinds remain variable, at 5 to 15 mph today, and drop to 5 to 10 mph tonight.

On Hawaii island, the more southerly winds may bring light amounts of volcanic smog, or vog, throughout the day and tonight. The windward side of Hawaii island is expected to be partly to mostly cloudy today and tonight, with brief, passing showers for the eastern and southeastern slopes.

Lava continues to erupt from a vent on the northwest side of Halemaumau Crater, according to the Hawaiian Volcano Observatory. The lava lake remained at 581 feet deep this morning, and thermal maps indicate the lake surface has dropped over the past two days. Reduced sulphur dioxide emissions were measured Sunday morning.

The large, northwest swell that begins tonight is expected to peak Tuesday night and early Wednesday before lowering gradually into Thursday. But a second, larger, northwest swell is expected to begin later Thursday.

These swells, forecasters said, combined with high astronomical tides, may cause coastal flooding for low-lying areas, particularly during early-morning high tides.

Surf for east shores drops from 5 to 7 feet this morning to 4 to 6 feet Tuesday morning. Surf for southern shores is expected to remain at 2 to 4 feet today and Tuesday.

A small craft advisory has been issued for Kauai and Oahu waters, effective from 6 p.m. today to 6 a.m. Wednesday.

Moderate to breezy trades are expected return just in time for New Year’s Eve on Thursday, forecasters said, clearing out any lingering vog and fireworks smoke from celebrations.