Dressing to stay warm at -40 isn’t as difficult as it sounds. For example, Apocalypse Design in Fairbanks (www.akgear.com) makes expedition parkas and bibs suitable for running the Yukon Quest at -60. Pair them thermal underwear, fleece under layers, a face mask (the parka has a great hood), good boots (e.g. mukluks, bunny boots, northern outfitters), and good beaver mitts and you can stand around at -40 for a long time. Remember that this is just insulation – so if you are cold it will keep you cold, but if you are warm it will keep you warm. Don’t be afraid to add chemical hand warmers as necessary.
Now that you look like the Michelin man, imagine what happens if you have to run up a hill, run to the front of your team to undo a tangle, or chase a dog team that is getting away. If you sweat, then your gear is wet and now you are in trouble. The challenge is to dress so you are comfortable riding the runners, or sitting on the “old musher” seat, but you don’t overheat when you have to get off and work for a while. The real challenge in severe cold is not to overheat.
My solution is to use the lighter Alpine Parka and Bibs with several under layers to add insulation when necessary. Minus 20 is pretty forgiving and if you work up a sweat you are uncomfortable, but generally not in serious trouble. With good synthetic gear (no down or cotton), if you stay active so you generate body heat, you are pretty much ok.
Minus 40 is much less forgiving. If you get wet, either because you sweat or you fall into open water, you have to work much harder to stay warm. You may even have to stop and build a fire to dry out. I haven’t camped in -60 yet, but I imagine there is even less room for mistakes. Remember it is much easier to keep something (yourself for example) warm than to warm up something that got cold. You have to stay on top of things.Keep 'em Northbound