It isn’t easy to get to Schweitzer—the closest major airport is in Spokane, Wash., about a two-hour drive, including a steep road with sharp switchbacks. The two fastest routes from Idaho’s capital, Boise, are 10-12 hours and involve going through either Washington or Montana.

There aren’t many shops and hotels right at the mountain’s base, and cell and internet service can be spotty in the area. Residents have to pick up their mail in the village.

But Schweitzer is in the midst of a dramatic transformation, aiming to become a destination resort. Last season it added seven runs and two lifts and joined the Ikon Pass, a 47-mountain destination ticket that gives members access to elite ski areas around the world, including Aspen, Colo., Jackson Hole, Wyo., Utah’s Deer Valley, Vermont’s Killington and Zermatt in Switzerland.

The resort village, with a year-round population of about 65, currently looks like a giant construction site, as the resort embarks on a multiphase rollout of residential development. An angled, contemporary glass-and-steel hotel and restaurant, designed by hip Portland, Ore., firm Skylab Architecture, is rising amid the more traditional alpine condos and lodges. The skeletons of new modern houses and townhouses bolstered by steel rods now inundate the steep slopes.

Demand for real estate is so high that there are currently no houses on the market for sale and only two condos—a stark difference from the 40-50 units for sale in the wider area at any given time in the past, says Patrick Werry, an agent with Century 21 Riverstone. Home prices have risen 40% over the past year in this resort village of about 700 homes.

“Everyone is trying to get on the bandwagon,” says Craig Mearns of M2 Construction, which has a three-year waiting list to even start building a custom house. Its latest spec project sold out in a month, even when prices increased from $550,000 to $950,000 for a unit.

What’s happening at Schweitzer is happening all over Idaho. The state is in the midst of a ski renaissance. As its resorts expand their ski terrain and add amenities, demand for homes is booming.

“Idaho is attracting people who want a smaller resort experience—the feel that other Western resorts used to offer but don’t anymore,” says Thomas Wright, president of Summit Sotheby’s International Realty.

Idaho’s ski resorts are scattered across the state and their characters are as different as the terrain that surrounds them, from the arid, celebrity-infused Sun Valley, to the insular, pine-tree dense village of Tamarack, north of Boise. All the way east is the wilder, remote Grand Targhee, in the Teton Range, located in Alta, Wyo., just on the border with Idaho. But the appeal of all these places is the same: low-key, uncrowded skiing with consistent snow.

Real-estate agents say the demand for ski resort homes is an offshoot of the demand for homes in Idaho overall, a movement fueled by the pandemic, with people looking for properties with more space and, in some cases, more lax Covid restrictions. (Idaho is currently in a hospital resource crisis because of its high rate of Covid.)

Idaho’s home prices have grown 42% in the past two years—twice the national average and the highest of all the states, according to Nik Shah, CEO of Home LLC., a down payment assistance provider.

“Most of my friends are like ‘Idaho, what’s there?’ My response is, ‘exactly—it’s because you don’t know about it,’ ” says Harmon Kong, a 57-year-old investment adviser from Lake Forest, Calif.

Mr. Kong and his wife, Lea Kong, fell hard last year for Tamarack and bought two places: a ski-in ski-out, three-bedroom, three-bathroom penthouse condo in the fall of 2020 for $1.8 million, and three-bedroom, three-bathroom chalet nearby for $1.28 million.

Mr. Kong was used to skiing at Heavenly Ski Resort in Lake Tahoe, Calif., which he likens to Disneyland because of the crowds. At Tamarack, he says the snow is routinely powdery, there are hardly ever lift lines and there’s lots of backcountry skiing.

Opened in 2004, then shut in 2008 due to bankruptcy, Tamarack is in the midst of a resurgence. The resort’s lifts currently service about 1,000 acres of skiable terrain and it has applied to the U.S. Forest Service for permits to add seven to nine new lifts, including a gondola, and more than double its size by adding 3,300 new acres of ski terrain and a new summit lodge.

Building is underway on ambitious, multiphase residential development projects, which will result in 2,043 residential units, including about 1,000 hotel rooms and a mix of condos, estate homes, townhomes, cottages and chalets. Tamarack is in the process of starting a charter school. The average sold price for a home in Tamarack, which has about 450 homes in all, has grown 80% over the past two years, according to the Mountain Central Association of Realtors.

To attract more skiers, this past year Tamarack joined the Indy Pass, which includes small, independent resorts around North America. The resort’s president Scott Turlington is aiming for 500,000 skier visits over the next couple of seasons (up from 120,000 last season), which he acknowledges might make him persona non grata among some of the current homeowners. “If I do my job properly I won’t be the most popular person,” he says.

Still, Mr. Turlington says, “We want to maintain our rugged individualism and independent spirit. It’s a very different feeling here than at one of the top resorts.”

The top ski resort in Idaho is Sun Valley. In fact, Ski Magazine readers voted Sun Valley the top ski resort in Western North America in 2021, in part because of its comparably short lift lines. It’s located in an arid, high-altitude and desert-like environment and its famed Sun Valley Lodge has walls lined with photos of celebrities like Marilyn Monroe, Ernest Hemingway and Tom Hanks. Business moguls and world leaders convene there every summer for the annual Allen & Company conference.

Sun Valley has also been growing its ski operations. Last season, it added 380 acres of skiable terrain on Bald Mountain and a new high-speed chairlift. It became a partner in the Epic Pass, which includes mountain resorts like Colorado’s Vail, Utah’s Park City and Whistler in Canada, a move to bring more skiers to the mountains.

Sun Valley Resort’s vice president and general manager Pete Sonntag says the resort has no plans to expand further for now. “Our goal is never about competing for the most skiers. It’s about improving the guest experience,” he says, adding, “The remote location will keep it from feeling overrun.”

But, like many resort towns, the issue of development and affordable housing is a hot topic right now. “There’s a huge concern about people getting priced out,” says Katherine Rixon, a real-estate agent with Keller Williams Sun Valley. Property values have appreciated so much that many owners of rental properties are cashing out of the market, leaving their tenants having to find a new place to live in an already tight rental environment. And at the same time, rental rates have doubled in the past year. There are a number of government and nonprofit groups working on increasing housing for the workforce, she says.

The number of sold homes was up 71% in August compared with a year earlier, the median price was up 20%, and the number of homes for sale down 56%. A three-bedroom, three-bathroom townhouse Ms. Rixon sold at Sun Valley last year for $2 million just resold for $3.6 million.

“People here complain when there’s four people in the lift line,” says Jean-Pierre Veillet, a real-estate developer. He moved with his family this summer from Portland, Ore., to Bellevue, about half an hour from Sun Valley’s main town of Ketchum, in part because his 15-year-old son Oliver is a ski racer and was attending a boarding school in the area.

Mr. Veillet, 50, and his wife, Summer Veillet, 45, bought a four-bedroom, two-bathroom, 3,000-square-foot house with a library, a three-car garage and a barn on 10 acres for $1.3 million in March. They’d been looking for a house in Ketchum and Hailey, the two towns in the area which are closer to the slopes, but gave up after not finding anything for a year.

Mr. Veillet still works in Portland, and even though that’s not far geographically, getting back and forth is strenuous because there are no nonstop flights to the small Sun Valley airport. The Veillets say there are pros and cons of living there: the skiing is great, Oliver is thriving, and their younger son, Zealand, who is 10 and is home-schooled, is getting a great education from the growing, fishing and renovating the family is doing.

On the other hand, the internet is terrible, there can be fierce windstorms and there’s no food delivery service. “It’s been a hard transition. It can be hard to slow down and make a change in life,” says Mr. Veillet.

David and Kimberly Barenborg just moved to Ketchum, into a five-bedroom, five-bathroom, over 4,000-square-foot log cabin-style house with a guest cottage in a quiet neighborhood right along a stream. They bought it for about $4 million in August after they sold their house in the Seattle suburb of Mercer Island.

Mr. Barenborg, 60, who co-founded a financial advisory firm, wanted somewhere that had sun, felt safe and where he could ski, bike and fish. “It’s just play time,” he says. “I’m so happy here.”

The only catch is the threat of development on a 65-acre dog park and green space that’s directly across the creek from their new home. He is working to help the town raise the $9 million the developer is asking for the property. He says the process has been slow going but the community is starting to see the value of protected green space. “Everyone is overwhelmed by what’s going on,” says Mr. Barenborg, referring to the rapid growth that’s stressing the town’s infrastructure.

The rapid growth is also increasing jobs, but Heidi Husbands, a council member in Hailey, says Sun Valley is currently facing a shortage of workers because people can’t afford to live there anymore. Ketchum approved funding for an affordable housing project, but it is still controversial. At one point the town considered allowing workers to put tents in a park, but that idea was canceled.

Some residents of Schweitzer are also worried about more crowds, traffic and a shortage of housing. The resort, owned by Seattle-based McCaw Investment Group, just sold out a 35-lot subdivision and broke ground on an addition to a condo building. In a few weeks, it will start building a new residential neighborhood with cabins before embarking on several others later next year. In five to 10 years, the resort plans a whole new area, with four new lifts and a new lodge.

The potential impacts from climate change are also an issue. Schweitzer CEO Tom Chasse says, “Strategically, we are concerned about the snow level. We are seeing a change in precipitation. The snow lines have been moving up for the last few seasons. So we want to make sure we have lift access to the higher elevations and we are doing feasibility studies on adding snow-making on the lower levels.”

However, Mr. Chasse says the resort has plenty of room to grow. “We want to increase our sophistication level,” he says.

Write to Nancy Keates at nancy.keates@wsj.com