Take I-89 across northern New England this time of year and you might see a squall turn that main route to Canada into a slippery streak of Wite-Out.
Today I am running northwest on another 89 that angles toward America's northern border: ITS 89, part of Maine's 13,000-mile Interconnected Trail System. The snow beneath me is unseasonably soft, and I'm sliding, but with a grin. That's the idea when you're snowmobiling through the North Woods on a groomed logging road.
My guide, Greg Caruso, gives a hand signal and stops. We shut down our Polaris FS Touring machines and climb off for a long look at Granny's Cap, a rocky outcropping covered with a thin evergreen shroud. The only sound: a muffled wind.
Snowmobiling - necessity for a few, deep-chill thrill for many, environmental hot button for others - has its epicenters. Maine is a major one. Snowmobile registrations crossed the 100,000 mark here for the first time last year, though national sales of new machines have been flat since spiking in a very white 1997.
The industry has piled on creature comforts in recent years, adding hand-warmers, reverse gear, and helmets with two-way radios to lure boomers of both sexes. New four-stroke engines are quieter and less polluting.
Coverage of ESPN's Winter X Games, which included snowmobile racing, could add youth appeal. And outdoor-sports facilities, including ski areas, have added snowmobile rentals as an option for adventurous first-timers and inveterate "slednecks" interested in sampling the latest toys without heavy capital investment.
In previous years, "we had little to offer in January, February, and March," says Russell Walters, president of Northern Outdoors, the resort that pioneered the local white-water-rafting boom in The Forks back in 1976. (The name refers to where the Kennebec and Dead Rivers meet.) In the mid-'80s the company bought a half-dozen snowmobiles - "sleds" to the initiated; now they have about 30.
Local clubs and businesses support the sport for the economic lift it brings. "We welcome trucks, sledders, and plain folk," says a sign in Caratunk, the town just south of The Forks. Every third vehicle up here is an F250-size pickup hauling a snowmobile trailer.
Trail networks are growing. Paper companies - Plum Creek alone owns 900,000 acres here - grant easements that are contingent on defined-trail use. All-terrain vehicles are forbidden. Neighboring states collaborate and compete with vast networks of connecting trails. A rider can even go international. Over the border in Quebec, Mr. Walters says, lie enviable superhighways of snow.
We ride about 50 miles today, looping behind mountains and climbing across the bumpy shoulder of one, Mt. Coburn (elevation 3,750 ft.). The ride down the far side is a controlled 40 m.p.h. dive through a glade of young pines. Sometimes the sledding has a rally-car feel, with sweeping turns. Other times it's more like horseback riding, padded saddle rising and falling.
But for non-enthusiasts, the sport raises questions about its environmental impact. The biggest debates over snowmobiles have concerned their use in Yellowstone. Decades back, the US Parks Service encouraged snowmobilers to ride near Old Faithful, says Ed Klim, president of the International Snowmobile Manufacturers Association in Haslett, Mich.
But concerns about the stress to bison have since led to a series of impact studies, including one now under way.
Some snowmobilers feel singled out. Many forest trails they use are open to loggers and recreational users during three seasons, says Mr. Klim. "The difference is that in the winter we're able to make arrangements to ride across the perimeter of farmland," he says. "Most farmers in the northern region of the US are snowmobilers. And they know that when we ride on top of the snow we don't do any damage."
That's debated. There are special places - including some national parks - from which all off-road vehicles are excluded, says Chuck Clusen, director of the Alaska National Parks Projects for the Natural Resources Defense Council. The wildlife issue is serious, he says. "I've seen big bison jump from a trail out into a snowbank," he says. "That really taxes them."
Then there's air and noise pollution, even limited water pollution that results from riders using frozen lakes. "We'd like to see manufacturers move more swiftly to the four-strokes and perfect them so they can get pollution levels down," Mr. Clusen says. "We recognize that snowmobiling can be a legitimate recreational activity," says the cross-country skier, who notes that most snowmobilers he encounters slow down and give him a wide berth. "Then there's that other 10 percent who go zooming by me at 60 m.p.h.," he says, "and the occasional one who will violate the law and go into the wilderness area."
"Most trails are on private land," says Laurie Bruce, a grandmother who has taught a safety course in Schroon Lake, N.Y., since the 1960s. "And most snowmobilers know that if you upset a landowner and they cut the trail off in the middle, you don't have any place to ride." Problems arise because of sleds with too much power, says Ms. Bruce, who rides a 1969 Moto-Ski - all of 11-1/2 horsepower. "Everybody laughs," she says. "But I can go down any trail, and if I get into trouble I just get off and flip it around."
I understand what Bruce means when my 650-lb. Polaris slumps into a trailside ditch as I negotiate a gully; it takes two men to dislodge it.
Other common trouble-triggers: alcohol, and riders who ignore thin ice. In the winter of 2002-03, 28 snowmobiling fatalities were recorded across Maine, New Hampshire, and Vermont - more than any of the previous 12 winters, according to a joint study by the three states.
State requirements for rider training vary. Manufacturers have been pushing a safety program, and responsible adventure companies do their part. Northern Outdoors, for example, created its own safety video. Guides brief new riders on safe following distance and keeping to the right - something park wardens have begun to enforce more rigorously.
Good riders self-police, too. Nearly every snowmobiler we encounter uses signals. We see almost no trailside trash. And the only off-trail tracks are from moose and, occasionally, hiking boots. We leave a set as we hike to a waterfall before we turn back for the lodge.
"I like to get out and explore," says Mr. Caruso. "And there are lots of areas you just can't get to any other time of year."
• There are four major manufacturers of snowmobiles: Arctic Cat, Polaris, and Yamaha in the United States; BRP in Canada.
• Last year, 100,899 snowmobiles were sold in the US; 46,304 were sold in Canada.
• 20 percent of owners use their snowmobiles for work or ice fishing.
• The average age of a snowmobile owner is 41 years old.
• 37 percent of snowmobilers are over 50 years old; 17 percent are over 60.
• The average annual household income for snowmobilers is $70,000.
• There are more than 230,000 groomed and marked snowmobile trails in North America, developed by volunteer clubs working with local governments and private landowners.
Source: International Snowmobile Manufacturers Association