The hike to Rainbow Falls in the Devils Postpile National Monument (near Mammoth Lakes, CA) is generally rated as moderate and is highly accessible for most families and casual hikers. The standard trail from the Devils Postpile ranger station is approximately 2.5 miles (4 km) one-way (5 miles round-trip). While the terrain is relatively flat with a gradual descent toward the falls, the "hard" part for many visitors in 2026 is the elevation and sun exposure. The trail sits at around 7,500 feet, meaning the air is thin, and much of the path travels through a "burn scar" from a previous forest fire, offering very little shade. If you take the shuttle from Mammoth Mountain Main Lodge, you can reduce the walking distance, but you should still be prepared for a dusty, sandy trail and a steep set of stairs if you want to go down to the base of the 101-foot waterfall. It is not a technical climb, but the heat and altitude can make it feel much more strenuous than a typical 5-mile walk at sea level, so carrying at least two liters of water is essential.