A high-surf advisory remains in effect until at least 6 p.m. today for the north shores of Oahu and Maui and the north and west shores of Molokai, Kauai and Niihau, the National Weather Service said.

Waves of 18 to 24 feet were expected, dropping to 14 to 18 feet later today.

The advisory replaced a high-surf warning that was canceled Thursday.

The weather service said strong currents will make swimming “difficult and dangerous.”

Surf along the west shore of Oahu was 12 to 16 feet, dropping to 8 to 12 feet today.

A large and “very dangerous” northwest swell also will produce harbor surges and large breaking waves in harbor entrances, the agency warned. The affected harbors include Waianae, Haleiwa and Hanalei, Kauai.

A small-craft advisory for Hawaii waters was set to expire at 6 a.m. today, with swells dropping below 10 feet.

On the Garden Isle on Wednesday, lifeguards rescued a Kauai man from the water off Lumahai Beach during very high surf and dangerous ocean conditions.

The 29-year-old Hanalei man was standing with a group of friends at the water’s edge when a large wave swept onto shore and pulled him in, Kauai County said in a news release Thursday. The strong current dragged the man beyond the breaking waves, which were reported to be up to 30 feet on the North Shore.

Lifeguards from the Hanalei Pavilion tower used personal watercraft and found the man roughly 300 yards offshore. The waves at Lumahai Beach were too large to bring him in, so he was brought to Black Pot Beach at Hanalei, where he was met by firefighters.

The man was in good condition and refused medical treatment.

“In this case the distressed swimmer did not attempt to fight the current and swim back to shore,” Ocean Safety Supervisor Kalani Vierra said in a statement Thursday. “He stayed calm and waited for help to arrive, which likely helped to save his life.”

As dangerous surf continues off northern shores, lifeguards are urging beachgoers to stay out of the water and away from the shoreline.

“A 20- to 30-foot wave will sweep up onto shore and easily knock onlookers off their feet,” Vierra said. “Being swept out to sea in those conditions can be deadly, and we are very grateful to our lifeguards, who have been working incredibly hard during this continued high-surf event to prevent tragedies.”

Officials are advising no swimming at any of Kauai’s north shore beaches, including Anini Beach. Lifeguards will reassess ocean conditions this morning, and updates will be given as information becomes available, the county said.

For up-to-date information about Kauai’s ocean conditions, speak to a county lifeguard, log onto kauaiexplorer.com or call the Ocean Safety Bureau at 241-4984.

On Maui, Hookipa Beach Park was closed Thursday due to high surf.

Meanwhile, it’s been hot all week.

On Wednesday it was 83 degrees in Lihue, tying the record for the date set in 1963. The mercury hit 86 in Kahului, breaking the old record of 85 set in 1993.

On Tuesday, Lihue had a temperature of 86 degrees, breaking the old record of 83 set in 1962.

Hilo on Tuesday tied the record of 86 degrees set in 1977.

Hilo also set a record high Monday at 88 degrees, and on Sunday, Kahului tied its record high of 88.

The weather service said a weak high-pressure system will stay in place over the state through today, resulting in light wind and minimal chances for rain. The tradewinds are expected return over the weekend as high pressure builds north of the state, increasing shower chances over windward and mauka areas.

Light wind is expected to return Monday as high pressure north of the state weakens, allowing showers to take shape over the interior of the islands mainly during the afternoon. Tradewinds will pick up Tuesday through Wednesday, with light wind returning by Thursday.