The biggest North Shore swell of the season so far started rolling in yesterday, and forecasters expect 25-foot wave faces to stick around through tonight.

Last night, as the waves were rising, rescuers responded to two surf-related incidents.

Rescuers said a surfer in distress was pulled from the waves at Alligator Rock on the North Shore late yesterday. It's unclear whether he sustained any injuries.

Also last night, rescuers were searching for a missing surfer at Kawela Bay on the North Shore, though authorities couldn't immediately confirm that the surfer hadn't simply left the beach without telling his friends.

The surfer was reported missing about 5:15 p.m., in 10- to 12-foot waves.

The Coast Guard, lifeguards and firefighters searched until sundown for the man last night, and could resume searching this morning.

The National Weather Service issued a high-surf warning yesterday for the north-facing shores of O'ahu, Kaua'i, Moloka'i, Maui and Ni'ihau through tomorrow. The surf started rising yesterday and will likely peak this afternoon.

Weather service forecaster Jonathan Hoag said the waves probably aren't large enough to endanger any beachfront properties or roadways. But officials are asking surfers and spectators to use caution. Hoag also said that the surf will likely get choppy this afternoon, when trade winds pick up a bit after a brief lull.

The weather service said the biggest surf from the weekend swell will likely be seen on Kaua'i. But all north-facing shores in the weather service warning will see monster surf. Forecasters expect most sets today to have wave faces at about 25 feet, but said some sets could have faces as high as 30 feet.

The high surf warning advises beachgoers of "dangerous, battering waves" that will result in very dangerous swimming conditions and "deadly rip currents."

The northwest swell was spurred by a strong low pressure system in the Pacific, Hoag said. Once the first swell dies down, a second swell is expected to follow, arriving Monday night and likely spurring another high-surf warning.

Meanwhile, the weather service also issued a high-surf warning for the west-facing shores of O'ahu, Kaua'i, Ni'ihau and Maui through tomorrow, with wave faces from 10 feet to 20 feet forecast through today.