If the truth be told at last, a foot of fresh powder and a short lift line do not alone bring joy to residents of Rocky Mountain ski areas. What makes them even giddier is the first blazing of wildflowers and the long mellow summer days that follow.
Everywhere you go in the Rockies, you are likely to hear the natives declare, ''I love to ski, but more and more it's summer that I look forward to. Fishing, hiking, biking, golf, tennis, ballooning - the athletic possibilities are endless, and at night there's always a concert or ballet or classic old movie.''
Of course it wasn't always so. Only a few years ago, ski-happy Westerners looked on summer as an intrusion on their beloved wintry way of life. Then a couple of snowless winters forced the ski resorts to make summer a more salable commodity. The fitness rage brought jogging, hiking, and kayaking into favor; culture took a grip on the high country, and all of a sudden many people from Taos, N.M., to Big Sky, Mont., and from Copper Mountain, Colo., to Park City, Utah, began to look on winter as the intrusion.
Up at Big Sky in southwest Montana this summer - the resort that Chet Huntley built - guests will be turned loose on the Gallatin River for rafting, kayaking, and fishing even as snow clings to the top of 11,000-foot Lone Mountain. Just seven miles down the road from the Huntley Lodge and ski area, the Lone Mountain Guest Ranch converts itself from a prime cross-country skiing retreat to a versatile and vigorous dude ranch. There are back-country hikes, barbecue supper rides, mule-drawn hay rides, trout fishing on the blue-ribbon Gallatin, or simple fireside relaxation in one of a dozen log cabins, some of which date to the 1920s.
Most surprising of all is the quality of dining, which might be called ''haute ranchwagon.'' Chef Neil Navratil, who doubtless would be working in some multi-star big-city kitchen if he weren't so smitten with Big Sky country, makes inventive soups and breads and does an occasional turn with flambeed meats and desserts at your rustic table.
Lone Mountain (Box 145, Big Sky, Mont. 59716) is always an education, whether one is on a nature hike or sitting in the lodge at night as Fred Donaldson, the house mountainman, puts on his bearskin fringe and gives a lecture on beadmaking and fur-trapping in the days of Jim Bridger, Kit Carson, and Jebediah Smith.
Nearer to Bozeman, Mont., the friendly little ski area of Bridger Bowl takes the summer off. But a quarter-mile away a cross-country ranch called Crosscut turns its attention to barbecues and hayrides, jogging workshops, and guided fishing excursions. Crosscut (PO Box 398, Bozeman, Mont. 59771), though saddled with somewhat makeshift sleeping quarters for the time being, has a handsome main lodge and puts on a fancy feed at all meals.
Jackson Hole, south of Bozeman, is of course no summer secret because of its proximity to both Yellowstone and Grand Teton National Parks. Still, the busy ski town is worth a visit - if only for a glimpse of the majestic Tetons, a day's run on the Snake with the veteran Barker-Ewing rafting company, or a performance of the Grand Teton Music Festival in July and August. Festival Hall is up at the Teton Village ski area, where you can ride the 21/2-mile aerial tramway to the top of Rendezvous Peak and imagine the chilling downhill runs a skier takes in winter. Teton Village also keeps open its excellent range of restaurants, such as the Alpenhof, the Mangy Moose, and the Sojourner.
Seventy-five miles west of Denver, Summit County's polyglot winter ski areas - Keystone, Copper Mountain, and Breckenridge - do an active summer trade. The plushly appointed Keystone has all the offerings of a flatland resort - a Robert Trent Jones Jr. golf course and a 14-court John Gardiner tennis ranch - to go with its Rocky Mountain specialties: riding, backpacking, and kayaking.
There is serious sailing on nearby Lake Dillon, but you can also glide about little Keystone Lake, hard by the 152-room main lodge, where on winter nights guests ice skate to taped music. From Copper Mountain and the revived mining town of Breckenridge, bicyclists can follow a 40-mile paved trail clear to Vail, a summer beehive as abuzz as Aspen, the queen of Rockies warm-weather resorts.
At Park City, Utah, 27 miles northeast of Salt Lake City, the old mining town turned ski resort will celebrate its centennial this summer as well as its 15th Art Festival. The art is displayed on Main Street, which is such an appealing block of period buildings that the entire strip is on the National Register of Historic Places. Park City and the Wasatch Range can perhaps best be appreciated with a bird's-eye view; helicopters, gliders, hang gliders, and hot-air balloons can all be employed for that purpose.
Just around the bend from Park City, Robert Redford's Sundance resort puts on a summer theater as well as film and theater workshops as part of the Sundance Institute. Nearer by, the posh new Deer Valley ski area doesn't miss a beat in the summer, pampering its guests with the Valhalla spa, complete with fresh seafood flown in from the Northwest.
For those summer snowbirds who can't do without the thrill of sweeping down a mountainside, Park City has the answer: The Alpine Slide, a banked and curving concrete funnel reachable by a chairlift and descended via plastic sleds. It's a half-mile run and not a mogul all the way.