Arizona is a lesson in extremes, a geographic wonder where you can enjoy all four seasons of the year simultaneously. Are you torn between skiing and a sun-splashed winter holiday? In Arizona, you can have both, and on the same trip.

Consider this itinerary: After a long weekend of guided cross-country skiing on the North Rim of the Grand Canyon, where winter snowfalls are heavy, you hurry south to Tucson for several days of inn-to-inn hiking beneath a Sonoran Desert sun.

Linking two such adventures is quite possible, in part because of the state's extremes in elevation. Winter can be harsh at the North Rim, where the thickly forested plateau rises to above 8,000 feet, but down in the desert around Tucson, at about 2,000 feet, mid-winter days generally are mild and sunny.

Arizona is an outdoorsy state, and skiing and hiking are among the diverse excursions put together by adventure tour organizers capitalizing on the state's natural beauty and its vast expanse of national forest and park lands. Other guided activities include backpacking, trail riding on horseback, mountain bicycling and white-water rafting.

All of these trips, including rafting, are offered during the winter or spring months when much of the rest of the country is too cold for them. Avid hikers and cyclists from up north flock to Arizona, say tour organizers, to get in shape for summer outings back home. And the North Rim draws cross-country skiers who want to see the Grand Canyon when its colorful walls are dusted in snow.

Indeed, winter and spring are the prime seasons for the state's guest ranches, and if you choose your travel dates carefully you can go trail riding when hillside cactuses are in bloom. April is about the earliest that raft trips through the Grand Canyon are scheduled, but you can sign up for a five-day trip down the Salt River as early as March 6.

Some of the adventure trips are as rugged as you will experience anywhere, but most are more easygoing. Generally, they are designed for active people who are fit enough to manage a moderate challenge, such as a day's hike or bicycle ride -- sometimes at high elevations.

At least two cycling outfitters have plotted tough uphill pedals from Sedona, in the heart of Arizona's Red Rock Country, to the historic mountaintop mining town of Jerome. Softies who figure they can't make the steep, five-mile ascent can always opt for a ride in the shuttle van that accompanies both tours.

The Sierra Club is offering a winter camping trip on skis to the North Rim of the Grand Canyon, and participants will spend four nights in tents on the trail. If that is rougher than you want, you can stay at cozy Kaibab Lodge just outside the national park boundary and ski to the rim on daily escorted outings.

Older travelers can enroll in a variety of Elderhostel classes on Arizona college campuses that require at least some modest outdoor exercise in the form of field trips to Indian ruins and other archaeological sites. Global Fitness Adventures is a week-long stress- and weight-reduction program centered on daily hikes in the pine woodlands surrounding Sedona. Regular massages are an after-trail reward.

Among Arizona's outdoor adventures:

Grand Canyon on skis. In winter, you can get to the remote Kaibab Lodge either by skiing, an arduous 26-mile challenge, or in the lodge's special "snow bus," a custom-made vehicle on tracks. This should give you some idea of the mountain solitude you will find on a cross-country skiing holiday.

Canyoneers Inc. of Flagstaff, an adventure outfitter, operates the North Rim Nordic Center from the large, rustic old lodge, which it owns. Built in 1927, the lodge is located just outside the North Rim entrance to the Grand Canyon at an elevation of about 9,000 feet. Snow depth customarily ranges from six to 10 feet. Guides offer day outings over miles of maintained ski trails to canyon rim viewpoints.

The lodge offers accommodations in eight two-person rooms, and there are inexpensive bunk beds in two eight-person yurts -- a sort of heavy Asian tent -- set up outside. A lodge room is $60 a night for two people; a bunk is $15 per person. Hearty meals served in the dining room are additional. Ski rental equipment is $9 a day.

The main lodge has a large and comfortable sitting room with a huge fireplace. However, the building currently is undergoing renovations to make it more suitable for winter stays, and there are some inconveniences. For the upcoming season, showers are not yet installed. But it is hoped that the large, glass-enclosed hot tub will suffice.

This year, the lodge will be open four nights a week -- Friday through Monday -- from Dec. 21 through April 1. The quickest way to get there is to fly to Las Vegas and rent a car. You catch the snow bus at Jacob Lake, a small resort town north of Kaibab Lodge. The charge for the snow bus is $60 per person for the round trip.

From June through October, guided day hikes from the lodge are offered in the Kaibab National Forest to remote canyon views.

For information: Canyoneers Inc., P.O. Box 2997, Flagstaff, Ariz. 86003, 800-525-0924 and 602-526-0926.

A desert hike. Dry, sunny days and mild temperatures are the springtime norm in the Sonoran Desert outside Tucson. Hikers on a week-long inn-to-inn itinerary will explore the hillsides and canyons of southern Arizona, often in the footsteps of Cochise and Geronimo, the famous Apache Indian leaders.

By careful planning, you could link a weekend of skiing on the North Rim with one of the Sonoran hikes, which are offered by Vermont Bicycle Touring, a long-established inn-to-inn cycling firm. Introduced last year, the firm's first winter hikes sold out quickly.

Accommodations include a Tucson inn, the Hacienda del Sol, where the view from the dining room extends 75 miles, and the very comfortable Grapevine Canyon Ranch in the Dragoon Mountains.

The cost of the Tucson trip is $1,299, which includes lodgings and meals. Air fare is additional. Departures are March 31, April 12, April 21, Oct. 27 and Nov. 3.

For information: Vermont Bicycle Touring, Box 711, Bristol, Vt. 05443, 802-453-4811.

Inn-to-inn cycling. For five days, cyclists tour the scenically spectacular Red Rock Country of Sedona, north of Phoenix. And then, having toughened leg muscles, they are shuttled to the South Rim of the Grand Canyon for a day-long, 14-mile hike into and back out of the canyon on the Bright Angel Trail.

This itinerary, put together by Timberline Bicycle Tours of Denver, mostly sticks to paved roads. You pedal from inn to inn while a van carries your luggage. Accommodations each evening are in comfortable cabins, lodges and inns. The roughest day of cycling is the long ascent to Jerome, but you can always catch a van ride up.

The cost of the trip is $725 per person, which includes six nights' lodging, breakfasts and dinners. Bicycles can be rented for $85. Departures from Flagstaff are April 14, May 19, Sept. 15 and Oct. 13.

For information: Timberline Bicycle Tours, 7975 E. Harvard St., Unit J, Denver, Colo. 80231, 303-759-3804.

Old West on horseback. If you are adventurous, consider a five- or six-day wilderness pack trip by horse into the Superstition Mountains east of Phoenix. For more comfort, however, you may prefer to stay at a guest ranch and limit your riding to daily outings and the knowledge of a roof rather than stars over your head at night.

Both options are available from American Wilderness Experience of Boulder, Colo., an adventure travel firm that represents dozens of independent tour outfitters in Arizona and elsewhere throughout the country.

The wilderness ride climbs from the desert, where the cactuses should be in bloom, into mountain canyons draped in pine. Along the way, the fairly rugged trail winds past 13th-century cliff dwellings of the Saludo Indians. For five days, the cost is $580; for six days, $675. A discount is offered for reservations made before Jan. 1. Departures from Apache Junction are Feb. 18 and 25 and April 22 for the five-day ride and March 11 and 25 and April 1 and 15 for the six-day ride.

The firm also offers daily or weekly packages at five Arizona ranches, two of which remain open year-round. The rest close in the summer. At the deluxe Wickenburg Inn in Wickenburg, west of Phoenix, activities include tennis, swimming and horseback riding. During the winter high season, the rate begins at $100 a day per person, which includes three meals and horseback riding.

For information: American Wilderness Experience Inc., P.O. Box 1486, Boulder, Colo. 80306, 800-444-0099 and 303-494-2992.

Fitness on foot. Kristina Hurrell, president of Global Fitness Adventures of Aspen, Colo., is an avid traveler and a marathoner -- two passions she has incorporated into a fitness program she offers at varying destinations throughout the world. Fairly regularly, she alights in Sedona because of its "incredible" beauty.

The emphasis of her week-long Arizona program is on stress and weight loss achieved primarily through extended daily hikes into the Sedona mountains and attention to eating habits. Meals as she describes them are nutritious and tasty but definitely not hearty.

Typically, guests arise at 6:30 a.m. for yoga exercises and a liquid breakfast of blended juice, bananas and wheat germ. Participants then set out on a guided half-day hike of perhaps six miles or a day-long hike of up to 18 miles, usually in quest of an archaeological site or a place of unusual scenic appeal. A full massage is offered every other day on return.

Accommodations vary, but may be in a lodge or in a private estate home with a swimming pool. Optional side trips to Jerome and Tuzigoot National Monument, an ancient Indian ruin, are offered. The program in Sedona is offered April 14 and 21. The inclusive price is $1,800 per person.

For information: Global Fitness Adventures, P.O. Box 1390, Aspen, Colo. 81612, 303-920-1780.

Wilderness archaeology. Elderhostel, an educational organization for people age 60 and older, has scheduled literally dozens of low-cost programs this winter and spring at college campuses throughout Arizona. Many of them focus on the history of the ancient cliff-dwelling Indians of the region as revealed at archaeological sites. And a few involve one or more field trips afoot.

Among the programs is one aimed, as the Elderhostel catalogue cautions, at "the active hosteler." The warning is necessary because several extended hikes of up to five miles are planned in wilderness areas of the Verde Valley about 90 miles north of Phoenix and 20 miles south of Sedona. Participants will study the environmental settings of ancient Indian cultures and assess the problems of vandalism at such sites.

The five-day program, called "Cliffdwellings and Red Rocks -- Exploring the Backcountry," is sponsored by Yavapai College of Prescott. Accommodations, however, will be in a new hotel recently opened by the Yavapai-Apache Indians on the tribal reservation near Montezuma Castle National Monument. The cost is $265 per person, which includes five days' lodging, all meals and classes. The program runs March 3-8.

For information: Elderhostel, 80 Boylston St., Suite 400, Boston, Mass. 02116, 617-426-8056.

A winter camp. For the hearty cross-country skier, the Sierra Club has planned a trip to the North Rim of the Grand Canyon that includes four nights in a tent. The trip leader plans the menus and buys the food, but you share in the cooking and cleanup.

The trip begins at Jacob Lake, where skiers board the snow bus to Kaibab Lodge. Accommodations the first and final night of the outing will be in the lodge's bunk bed yurts. On the second day, you ski into the park and establish camp near the Grand Canyon Lodge, which remains closed over the winter. One park ranger is on duty, however, at the nearby North Rim ranger station.

Participants will carry 35-pound packs containing food, fuel, cooking gear and tents to be shared. The trip is limited to 13 skiers, two assistant guides and the trip leader, Tom Stricker of Atlanta. The cost is $495 per person, which includes all meals, plus $60 for the snow bus.

For information: Sierra Club, Outings Department, 730 Polk St., San Francisco, Calif. 94109, 415-776-2211.

Back roads by bike. On this five-night, six-day bicycling trip in the Sedona area, you pedal mountain bicycles mostly on dirt back roads maintained by the U.S. Forest Service.

Organized by Backroads Bicycle Touring of Berkeley, Calif., the itinerary takes in Sedona, the steep climb to Jerome and Montezuma Castle National Monument. Accommodations include Los Abrigados, a first class resort in Sedona, a pair of modest old hotels in Jerome and woodland cabins at Mormon Lake.

The cost of the trip from Flagstaff is $968 per person, which includes lodgings and most meals. Bike rental is $109. Departures are scheduled for May 12, 19 and 26; June 2 and 9; and Sept. 15, 22 and 29.

For information: Backroads Bicycle Touring, 1516 5th St., Suite H232, Berkeley, Calif. 94710-1713, 800-245-3874 and 415-527-1555.

White-water thrills. Early spring is rafting season on the Salt River, which forms the boundary of two Apache Indian reservations. The Salt River Canyon northeast of Phoenix isn't as famous as the Grand Canyon to the north, but a ride down its rapids can be as exciting. They are rated as rough as the white water of the Grand Canyon.

Outfitter Bill Dvorak of Nathrop, Colo., has organized a series of five-day, four-night rafting and camping trips on the Salt River. You travel in paddle boats -- inflated rafts in which everyone paddles -- or in oar boats in which the guide does all the work. The rafts are put into the river where it is crossed by U.S. 60 about 30 miles north of Globe, and the ride ends near Theodore Roosevelt Lake to the west.

The cost from Globe is $500. Departures are March 6 and 20, April 17 and 24 and May 1, 8 and 15.

For information: Bill Dvorak Kayak and Rafting Expeditions, 17921-WP, Highway 285, Nathrop, Colo. 81236, 800-824-3795 and 719-539-6851.

For a list of outfitters licensed to run the Colorado River through the Grand Canyon contact the Office of the Superintendent, Grand Canyon National Park, P.O. Box 129, Grand Canyon, Ariz. 86023, 602-638-7888. A seven-day trip from Lee's Ferry near Page to Pearce Ferry near Las Vegas is about $1,200 per person.

Day trips From Phoenix. Even a business traveler with only a half day of free time to spare can enjoy a guided hike into the mountains near Phoenix. The Open Road, a Phoenix sightseeing company, offers half-day and full-day hikes year-round. In the summer, however, you get an early start to avoid afternoon heat.

The half-day hikes to Squaw Peak and on South Mountain provide impressive views of Phoenix. The fee is $35 per person, which includes a snack and use of a day pack and water bottle. The full-day trips explore Sedona's red rocks or the Superstition Mountains. The cost is $65, and lunch is provided.

For information: The Open Road, 1622 East Gardenia St., Phoenix, Ariz. 85020, 800-766-7117 and 602-997-6474.