On many western rivers, prime rafting season is spring, when snowmelt from the high country feeds the rapids and a dunk will leave you hypothermic. Then, just when the weather's getting hot enough and the kids are finally out of school, the flows drop too low to float a boat. Oh, the irony.
But some rivers, like the Smith in central Montana, a which flows to the Missouri, hold their water well into summer. Renowned as one of Montana's finest trout waters, the 59-mile stretch of Class I-II rapids through Smith River State Park makes a terrific four-day family fish-and-float trip. Peak season is June 15 through July 15, and some years, depending on water levels, it's even boatable into September. Two weeks ago, water temperatures soared to a nearly tropical 78 degrees: too hot for fishing (the native brown and rainbow trout can withstand 73, max) but perfect for swimming.
From the put-in at Camp Baker, near White Sulfur Springs, you drift through a remote wilderness canyon in the Big Belt Mountains, with shady stands of ponderosa pine and Douglas fir and 2,000-foot limestone walls in places—all of it off limits to motorized watercraft. Because the river passes through a patchwork of private ranches and Forest Service land, camping's permitted at designated sites only, which you must reserve in advance. Request Paradise Bend, on a bench just below a meadow ablaze with wildflowers, and allow time each day to wander up side canyons in search of Native American pictographs and cast for trout. While there are only several Class II rapids, all within the last 15 miles, the Smith River is twisty and narrow; sharp corners, sheer walls, and river snags make this a tricky run, even if it's not technically whitewater.
DIY: Private permits are awarded by lottery; out of more than 6,000 applicants, only 1,000 get launch dates. Applications are accepted in January, but if you get shut out, you may still be able to nab a last-minute launch date by calling for cancellations. From May 15 through July 15, trips are limited to four nights. Typical summer flows are around 300 cubic-feet-per-second, but they can drop depending on the irrigation demands upstream; 250 cfs will float a 14-foot raft. Below 150, you'll need a canoe or kayak, or else you'll be dragging your raft through the shallowest sections.
Outfitters: Glacier Guides runs five-day family trips on the Smith. A handful of commercial guide services like Lewis and Clark Expeditions and Missoula Fishing Company lead fishing-focused raft adventures.