I'd think a winter down parka from REI or some such, with only a thinnish synthetic layer under. Down is amazingly breathable. One adjusts effort to prevent getting either sweaty or cold. Expensive though. You want a thin outer and inner of ripstop, and not sewn-through construction. Another approach is to wear a somewhat oversized cycling wind jacket (not waterproof or resistant!) for the top layer, a poly zip-tee next to the skin, like from Craft, then a layer of 100, 200, or 300 fleece depending on temperature and experience. There are also wind jackets made for hikers and climbers which have a hood. Again, nothing water repellent. You can tell if it's the right wind jacket by putting your mouth on it and seeing if you can suck air through the fabric, but only slowly. When I delivered papers on foot in Fairbanks, I made a point of not adding more or warmer clothes until I felt my skin cold under my clothes. That forced me to adapt and be OK with what I had available when it got down to -60. One does adapt to cold as well as to heat.
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