By Matt Furber for the New York Times, FEB 25, 2014 – . Snow has been so scant in Idaho this winter that bicycles started showing up in shop windows in the middle of January, and cyclists began booking ski huts during a season when it’s usually backcountry skiers who are seeking accommodations. What may be bad news for skiers has turned out to be an irresistible opportunity for those who love to ride on mountain bikes with four- and five-inch-wide tires, which are designed to float over snow and sand and still provide substantial cushion for rough single track (even without the suspension common to many bikes with skinnier tires). Where trails are too soft for regular mountain bikes, or too sparse to protect skiers from subsurface obstacles, fat bikes are filling a gap. Riders do well on mixed terrain, including on trails where the snow is too thin for skiing and on south-facing pitches where dirt is exposed during a low-snow winter. “It’s opening a new way to be outdoors,” Chris Estrem, a Ketchum physical therapist, backcountry skier and world bicycle traveler, said. “It’s made me a better mountain biker. I want to ride it all the time. I love it.” Tory Canfield, who started an organization called the Fat Bike Advocacy Group, said: “For me, fat biking on snow creates a sense of ethereal floatiness that conjures up the sensation of powder skiing. As soon as your tire rolls forward, your mouth turns up into a big, fat grin. It is nothing short of fun.” The weather that has made for optimum fat-tire biking may be around for a while, Charles Luce, a Boise-based research hydrologist for the United States Forest Service, told me. “Precipitation has been declining in the region, and the probability of severe droughts has been increasing over the last 60 years,” said Mr. Luce, who co-wrote a paper on the subject that was published last December in Science magazine. “One of the key physical drivers for future precipitation, westerly wind, is also expected to decline on average in the future.” As a longtime mountain biker who finds peace in remote trail riding, I decided to experience the winter “fat bike” phenomenon for myself and took a road trip from Boise to test bikes in some of the state’s mountain haunts. It has been cold in Boise, which is 2,700 feet above sea level, but that hasn’t stopped riders of fat bikes, especially when it comes to fat-bike trials, including an event organized by Fat Bike Boise in early December (a celebration of Global Fat- Bike Day) on a thin layer of early snow preserved by the cold. It should be said that Boise on any bicycle is a compelling starting point for an adventure. Hotels and restaurants are a brief ride from the airport, and trailheads are a short distance from downtown. In Idaho riders learn to roll through stop signs, maintaining guiltless momentum on the way to places like Zoo Boise to see snow leopards because a 1982 rule dubbed the “Idaho Stop Law” permits cyclists to treat stop signs as yield signs. The first higher elevation stop on my biking quest was at 3,900 feet in Salmon, an outpost for the Continental Divide Trail, at the confluence of the Lemhi and Salmon rivers. Roads there wind through crinkled mountains that begin near places like the phenomenal lava fields of Craters of the Moon and rise to the north above the Snake River Plain that is bent like a fishhook through the southern part of the state — a dramatic landscape by any route. Salmon is a hunting and recreation gateway on the edge of the Frank Church-River of No Return Wilderness, a town steeped in Western lore and known as the birthplace of Sacagawea. My trip began at the Hub, a new bike and ski shop a block off Main Street that also serves pizza and beer. There I met the owner, Max Lohmeyer, a Fruita, Colo., native and lifelong mountain biker, who would take me for an evening ride on Discovery Hill. After exiting Mr. Lohmeyer’s van at the trailhead, we crunched on our bikes over thin patches of snow turned ice luge in some sections. In the dark, chips of snow that shot from the front tire glowed like welding sparks as they floated through the bright beam of my bike light. Traction on marginally snow-covered trails varied with pitch and aspect. Navigating surfaces and slopes was more fun than it may sound, which I attribute to the novelty of riding a super-fat mountain bike tire under the shine of a full moon. At times during our ride, some 13 miles through mountain desert country with the Salmon photographer David Lingle, we could see the lights of town below. Back at the trailhead another rider left a note on Mr. Lingle’s car, a calendar photo of two emperor penguins standing together in the grass. One bird, craning its neck, had a scribbled dialogue bubble above it that read, “Just call me Master of the Moonlight! Bahahaha.” Later, at dinner at the Junkyard Bistro in Salmon, where the special was an Idaho burrito with mashed potatoes and bacon, the conversation was, inevitably, about fat bikes. “I’ve never seen a trend come on so fast,” Mr. Lohmeyer said. (So much so that the first-ever U.S. National Fat Bike Championship will be held March 8 in Cable, Wis.) In bed after enjoying the frontier night life, which included watching outdoor hockey, my mind continued to slip and slide — I was hooked on riding in the snow and excited to try it in the daytime too. To get to my next destination I drove through the wide valleys of the Lost River and Pahsimeroi mountain ranges to the Teton Valley, which has a large contingent of snow-sports people in the towns of Victor and Driggs. Snow biking is managed in conjunction with Nordic skiing at the base area of the Grand Targhee Resort at 8,000 feet in Alta, Wyo., and just over the border