As spring gives way to summer, there are still high places we want to get to with cold air and wild variations in temperature. What we need is a jacket that can operate smoothly across a range of temperatures and exertion levels, and that doesn't slow us down.
The Patagonia Nano-Air does all of that, and as a boon backcountry companion it's hard to beat - with just a couple of caveats, but first the good stuff, which is very, very good. The Nano-Air is ridiculously light for a jacket that insulates this well, just 13.6 ounces. The insulation, Patagonia's own FullRange synthetic rated at 60CFM air circulation, also performs unbelievably well over a really wide range of conditions, from well below freezing to well above, at an equally wide range of aerobic output. You'll end up adjusting layers a lot less with the Nano-Air.
The jacket compresses very small, much smaller than you would believe possible given the amount of loft in the insulation. In fact, all the materials are top-notch even by the high standards we've come to expect from Patagonia. The mechanical stretch in the shell and liner is just awesome. Combined with an articulated cut the Nano-Air just moves with you without you ever having to think about it.
Feature-wise it hits just about the full tick list: hand pockets are above harness level, there's two externally accessible chest pockets, and the hood fits over low volume helmets just fine. The main zipper has a full-length draft flap, with a mandatory zipper garage at the top. The only adjustments are the dual hem drawcords, and it's a tribute to the Nano-Air's design that we never noticed a need for any other adjustability. Of course the elastic cuffs and hood opening help here too.
The caveats are few but may be important to certain users. The only major one is that the same stretchiness that makes the Nano-Air wear so comfortably can work against you if you catch it on anything sharp, a possibility that is made more likely by both the bunchiness of the material and the facts that it is thin with high traction. For snow travel or non-contact sports, no problem; for rubbing against rocks, you'll want something else, especially if you're one of those people who are hard on equipment - you know who you are. The minor nits: a dual-action belay-friendly main zipper would be nice, and while you're at it throw in a couple of interior open mesh stash pockets.
In the end, for applications that don't require contact-proof equipment, the Nano-Air Hoody is a fantastic jacket that just might allow you to get rid of a couple of other layers. Stick a weatherproof shell over it and you're prepared for just about anything Mother Nature might throw your way.