Across the United States, the leaves are about to turn, and it's a performance that is always worth attending. The traditional show, and by most accounts the best, is in New England, where the forests begin to brighten as early as mid-September.

Altitude as well as geography are factors in the timing (the higher the altitude and the more northerly the location, the earlier the show), and this year drought in some areas may hasten the arrival of the colors. But foliage in the mountains of the mid-Atlantic should be at its most colorful from mid- to late October.

The usual way to see the leaves near Washington is to take Skyline Drive through Shenandoah National Park. The sights are as grand as the roadway is jammed.

Among the other scenic possibilities, here and elsewhere in the East:

*Take a short hike on the Appalachian Trail: The famous trail parallels the Skyline Drive, and access to it is fairly easy. You won't cover as much distance as a motorist, but you'll probably have better views. And you get to crunch the dry leaves under your feet.

*Ride a mountain-climbing train: A state-operated, steam-powered Shay engine hauls passengers up a former logging trail to Bald Knob, second-highest point in West Virginia. Saturday and Sunday through October (except Thursday through Sunday the first two weeks of October). Departs at noon for a 4 1/2-hour round trip; adults $9.50, ages 5 to 11, $4. Or there are two-hour trips to Whittaker Station at 11 a.m. and 1 and 3 p.m.; adults $7, children $3. In Cass, W.Va., (304) 456-4300.

*Cruise the New England Coast: The Pilgrim Belle, a 49-cabin coastal liner, sails from Hyannis, Mass., via the Connecticut shoreline to the Hudson River and the Catskills on seven-day foliage cruises. Departures Oct. 6 and 13; from $875 to $1,575 per person. Coastwise Cruise Line, P.O. Box 1630, Hyannis, Mass. 02601, (617) 778-6996.

*Cycle the Blue Ridge Parkway: It's a two-day mountain and valley trip, with accommodations at Rodes Farm Inn in Wintergreen Valley, southwest of Charlottesville. The price is $165 per person, including two meals daily (bike rental extra); Oct. 11-13. Bike Virginia, P.O. Box 203, Williamsburg, Va. 23187-0203, (804) 253-2985.

*Take in a fall apple harvest festival: Watch apple butter-making; sample fresh cider, apple pies and cakes; and enjoy mountain music and entertainment surrounded by the spectacle of the leaves. The big festivals are at Winchester, Va. (Sept. 21-22); Gettysburg, Pa. (Oct. 5-6 and 12-13); Thurmont, Md. (Oct. 12-13) and Berkeley Springs, W.Va. (Oct. 12-13).

*Spend a weekend at a mountain inn: You can savor the colors at leisure just outside your door. Take your pick of inns in Vermont, Pennsylvania, West Virginia, Virginia (or wherever) from numerous guides to country inns, available at local bookstores. But make reservations quickly, because they fill fast in the fall.

*Go trail riding along Virginia's Naked Creek: Guided day-long or overnight horseback rides begin at Mountaintop Ranch near the town of Shenandoah in the Blue Ridge Mountains, and there's always a stop at the falls of Naked Creek. Weekends into November. A day ride is $49 per person, including lunch; an overnight in a three-sided shelter with bunks is $165, including four meals. Mountaintop Ranch, c/o 2612 Shelby Lane, Falls Church, Va. 22043, (703) 560-6083 or (703) 298-9542.