Each Sunday morning hundreds of lake-loving faithful park their cars in a grassy field here that once hosted a drive-in movie theater. Some sync their radios to the religious service held on the stage ahead, while others pull out lawn chairs to enjoy a church that defies the summer slump of its urban neighbors.

Drivers toot their horns during key refrains of a hymn. Ushers take up the collection with fishing nets. Folks in the communion line bend over to pet pooches along the way.

“Our attendance just about doubles in the summer,” said the Rev. Kristin Oltmann, pastor of Crosslake Lutheran Church, who oversees a crowd that can swell to more than 500 — in a town of 2,200.

“I mentioned it to a [Twin Cities] pastor and she said, “So that’s where all our people are on Sunday mornings!’ ”

Call it reverse migration. As Twin Cities churches lament their empty pews this time of year, the metro faithful can be found in lakeside towns, North Woods chapels and traditional churches courting the flip-flops and shorts crowd. For places like Crosslake Lutheran, and more traditional churches, the warm weather blows in a steady breeze of believers.

Twin Cities clergy report summer attendance declines of 10 to 40 percent. Churches nationwide average a 25 percent drop from January and February to the dog days of summer, according to the National Congregations Study at Duke University. Minnesota, with its cabin culture and brief balmy season, may be even harder hit.

“It’s not just because of vacations,” said Duke sociology professor Mark Chaves, director of the Congregations Study launched in 1998. “School is out. The choir takes a break. There’s no Sunday school. There’s a different rhythm.”

Church consultants even advise clergy to remove some pews to make the place look more full, to merge Sunday services and add something new. Edina Morningside Community Church, for example, cancels three Sunday services in July and replaces them with Wednesday night outdoor gatherings, said the Rev. Oby Ballinger.

“There’s always competition, but there’s a lot more in the summer,” he said.

Cabin culture Jesus

Stop by a tourist information office in vacation meccas such as Brainerd or the North Shore, and you can find a list of houses of worship. Resort or grocery store bulletin boards display Sunday options.

Not all churches listed are booming. But those that court newcomers, are visible from major highways or have ties to a Twin Cities church seem to have an edge.

For example, Timberwood Church in Nisswa is part of the Wooddale megachurch in Eden Prairie. Launched in the Nisswa Community Center in 2004 with several dozen members, it now occupies a new 700-seat complex tucked in the woods off a major highway.

The growth is driven by full-time cabin residents, said the Rev. John Just, but boat-loving summer visitors contribute to the boom. The tourists, in fact, take the place of church members who travel elsewhere.

After a recent Sunday worship service, Just and about 75 church members revved up their boats and took off for a progressive lunch at three homes on Gull Lake.

“We’re visiting from Bloomington,” said Betty Selness, mingling with guests on the lakeside lawn. “I like there’s a year-round community and you can just blend in with it.”

Some churches, such as Crosslake Lutheran, organize special events such as Memorial Day aircraft flyovers and Classic Car days. It thrives on both full-time cabin-goers and visitors — many with surprisingly deep roots in the area. Second- and third-generation families, enjoying the cabin grandpa built, are not unusual, she said. Sunday morning church is part of that tradition.

“The cabins are gathering places for families, and of course, they bring friends,” said Oltmann.

The visitors don’t just show up on Sundays. Some lend time and talents that otherwise would benefit churches back home.

“My husband ushered at the outdoor service for many years,” said Marlys Thorsgaard, of Bloomington. “I used to go to Friday Bible studies. Our three grandchildren went to the Crosslake preschool Bible camp.”

Just this month, Thorsgaard could be found folding Sunday bulletins in the church office. Said she: “Church is important to me.”

Courting the faithful

St. Peter the Apostle Catholic Church in Park Rapids is among those that actively reach out to the camping and cabin crowd. It sends fliers to area resorts, said the Rev. Tom Friedl, and also advertises in some tourist publications.

The result: The barely 300 souls who show up for January services get a boatload of company in July. Said Friedl: “We had close to 750 last weekend at both places.”

Friedl was referring to a second location opened in the summer at Our Lady of Lourdes grotto in the town of Two Inlets. It’s a tranquil outdoor setting, but it requires the faithful to confront a summer evil — mosquitoes.

Before the service, a worker pulls out the fogger and blasts the place with bug repellent, he said. A fan is set on the floor of the makeshift altar to blow insects off the priest.

“We try to make it as comfortable as possible,” said Friedl. “Does it get hot in the grotto? Yes. Does it get hot all day in a fishing boat? Yes. You have to put it in perspective.”

Summer finances

The surge in visitors doesn’t always mean more money in ushers’ baskets. Church leaders say vacationers don’t give as much as regular members.

There are exceptions.

“One time we received a check for $15,000,” said the Rev. Steve Laflamme, of Holy Spirit Catholic Church in Two Harbors and St. Mary’s Church in Silver Bay. “We’ve received $5,000, $1,000.

“It doesn’t happen often, maybe a couple times a year,” he said. “But it’s staggering.”

Also staggering is the number of unfamiliar faces in the pews. “Sometimes I have more strangers than people I know,” said the Rev. Gabriel Waweru, of Blessed Sacrament Parish in Hibbing.

However, Waweru embraces the moment, thrilled that others agree “there is no vacation from God.”

Graying churches also enjoy a demographic shift: The summer crowd often shows up with youngsters in tow. Said Friedl: “It’s refreshing.”

Although tourist season is still at its peak, religious leaders here know the crowds soon will contract — and Twin Cities churches will swell again with the start of school year.

“We always feel a little sad when the outdoor worship is done for the summer,” said Oltmann. “But we look forward to it starting again.”