The largest challenge in trying to hike the entire Great Western Loop in a single continuous push is avoiding the winter. While I am a fairly experienced winter traveler, the winter conditions found along much of the Great Western Loop—namely the 4,700 miles of high-country between California’s High Sierra and Colorado’s San Juan’s—are simply not conducive to long-distance hiking: blizzards, avalanches, and route-finding difficulties would slow or halt progress frequently, and they would cause major safety concerns.
The solution to this challenge, then, is entering the high-country as early in the spring/summer as possible (a date that is based both on this winter’s snowpack and on my early-season skills and comfort) and exiting the high country sometime before the first winter blizzard. The remaining 2,200 miles can be completed mostly year-round, though it’s important to factor in some local issues like water availability, temperatures, and wintertime snowfall.
Only in early-March did I decide when and where I was going to start, and what direction I would travel. At that point the winter snowpack trends seemed sufficiently clear: the entire state of California, particularly SoCal, received drought-level precipitation this winter. Implications include: surface water in the arid areas will dry up quickly; low snowpack in the high-country will allow an earlier-than-usual entry; and wildfires will probably be severe and will start early. Meanwhile, northern New Mexico and southern Colorado have received above-average precipitation this winter. The two contrasting situations made my decision easy: go clockwise, and go early.
As for a starting point, Grandview Point in Grand Canyon National Park is a worthy place, understatedly. From there, I will have about a month to traverse the Sonoran and Mojave Deserts, where temperatures will be less than their summer peaks and water availability will be limited but better than it would be in the Fall. After I exit the San Juan’s in mid- or late-September, there are 1,000 more miles in New Mexico and Arizona before returning to Grandview Point; many of these miles will be dry, but the Fall conditions and high elevations should make it feasible.