That will be a great trip. The Colorado Trail stretches almost 500 miles from Denver to Durango. It winds through the Rocky Mountains in Colorado, traversing six wilderness areas and eight mountain ranges at heights of up to 13,334 feet. In fact, most of the time youll be 10,000 feet or higher. That means nights can be chilly, especially if youre still on the trail after mid-August.
That said, it wont be frigid. If youre a cold sleeper, a bag rated to 20 degrees would be more than adequatewarm enough for cold nights, but not so toasty youll poach when the temps are higher. At the pricier end for a bag such as this youll find Feathered Friends estimable Swallow ($349; featheredfriends.com), rated to 20 degrees with a water-repellent EPIC shell. It weighs just two pounds and is an excellent bag. Western Mountaineerings Alpinlite Super ($385; westernmountaineering.com) weighs just a touch less than the Swallow and offers a little roomier cut than most mummy bags. For something more affordable, REIs Sub Kilo +20 bag (rei.com) sells for $239 but is on sale now for $160. It uses good-quality down, has an excellent polyester shell, and weighs one pound, thirteen ounces.
Otherwise, a bag rated to around 30 degrees should do nicely. I like Marmots Arroyo ($249; marmot.com), an 800-fill down bag that weighs one pound, eleven ounces, uses Marmots excellent silicon-finished nylon shell, and has a snug-fitting hood. Or, Mont-Bells U.L.SS. Down Hugger #3 ($270; montbell.com) is a super-light (one pound, seven ounces) bag that uses Mont-Bells proprietary stretchy shell to gently hug" you as you sleep. That helps reduce cooling that occurs when you thrash around and force warm air out of the bag. Im using this Mont-Bell bag on some trips this spring and really like it. Sierra Designs Osage ($179; sierradesigns.com) uses slightly less fluffy down and heavier materials; but the result is a 30-degree bag of reasonable cost that still weighs only two pounds, four ounces.
Note that Ive mentioned all down-fill bags. For a trip such as yours I think thats the ideal material;light and warm. One synthetic option is the North Face Cats Meow ($169; thenorthface.com), which uses Polarguard Delta fill, has a temp rating of 20 degrees, and weighs two pounds, ten ounces.
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