It was a weekend for diggin’ the blues.

The North Atlantic Blues Festival in Rockland lived up to its name as summer rain and fog blew in from the north Atlantic Ocean on Saturday but not hard enough to chase away the fans.

Sunday broke misty as well, but by the time opening act Daniel “Slick” Ballinger took the stage the fog had lifted, allowing blues lovers once again to see the city’s symbolic lighthouse on the Rockland Breakwater, passing sailboats and the Penobscot Bay islands beyond.

Despite the need to slip on the slickers and pop the umbrellas, participants at the 15th annual festival hardly let the weather dampen their spirits. There was no lightning to send them running for cover, but there was plenty of electricity in the air as the performances by some of the leading blues acts in the country had people stomping their feet and rocking with the rhythm.

“Blues fans are true fans. They’re music fans, and they’ll come out for a show no matter what the weather is like,” festival founder Paul Benjamin said Saturday as rain pelted down. “We’ve had rain before, but nothing like this. But the die-hard blues fans are here, and we’re here to make some music.”

Consider Nick and Cindy Gregory of South Thomaston. Blues festival regulars, the Gregorys were at Harbor Park at 5:30 a.m. Saturday looking for choice, stage-front seats but were told to come back at 6 because the grounds were closed.

“We love it; we wouldn’t miss it for anything,” said Cindy, who had a piece of yellow police caution tape wrapped around her neck to hold her poncho in place. “We don’t care about the weather; we’re blues fans.”

The festival has taken on a life of its own since 1990 when the first festival was held in the parking lot of a nearby motel and attracted about 100 fans. Eddie Shaw and the Wolf Gang (blues legend Howlin’ Wolf’s former band) played that first festival and were back on the bill Sunday as well. Shaw got to know Benjamin when he played a gig at the Golden Spike, an old warehouse next to Rockland’s Maine Central Railroad tracks, in the late 1970s.

“I love Rockland. I’ve been coming here for 25 years, so it must be all right,” Shaw said Sunday. “I created this festival with Paul, played the Black Pearl for Virginia Larsen. I’m glad to see this thing grow from the time we roped off the parking lot at the Trade Winds to what it is now. It’s great. It’s a great place to play the blues.”

From those humble beginnings, the North Atlantic Blues Festival has grown to become one of the premier summer events on the blues circuit. Last year, the festival drew 16,000 fans to this city of 7,500 residents.

Chip Eagle, publisher of Blues Review magazine and online counterpart, Blueswax.com, produces blues festivals all over the world. Eagle described the Rockland festival as “one of the greatest” on the planet. He said the waterfront setting and strong lineup of acts cannot be topped.

He said Benjamin and his partner Jamie Issacson were viewed as icons within the blues community. He said Benjamin played a key organizational role in this year’s W.C. Handy Awards (the blues Grammys) in Memphis, Tenn.

Eagle said that playing the Rockland festival was a goal for musicians looking to build their reputations. A number of today’s stars, such as Shemekia Copeland, had their breakout performances in Rockland. He cited the 21-year-old Ballinger as someone on this year’s bill who has a promising future. Rockland can do that for a performer, he said.

“It couldn’t be in a more beautiful setting,” Eagle said Sunday. “You can step off the back stage right into the ocean. The people of Rockland are great, and they love the blues. The blues is a tribe of people all over the world, and we have a few tribal gatherings. This is the only place in New England where the tribe can meet.”

Not only do the bands play two days straight at the festival, they also spend their offstage nights entertaining in local bars and restaurants during the popular Friday and Saturday night “Club Crawl” and Sunday night jam session.

Benjamin noted that advance sales for this year’s festival were 10 percent above those of last year. Although Saturday’s turnout was down, the break in the weather Sunday lured twice as many fans to Harbor Park for the show.

“I think we’ll have another successful year,” he said. “Obviously, the weather will keep some people away, but these fans can’t get enough of this music. And they love coming to Rockland.”

Tom Nyrick of St. Petersburg, Fla., is one of those who can’t get enough of the blues. Nyrick said he always tries to time his Maine visit with the dates of the blues festival. He has attended festivals in Florida but said nothing can top the North Atlantic Blues Festival in Harbor Park.

“This place has its own feel,” said Nyrick. “It’s really unique. It’s not generic by any means.”