Modified from:
http://www.pmags.com/joomla/index.ph...owshoeing.html
A quick and dirty rule of thumb is to use the
20 Degree Rule. Borrowed from running, it simply means to dress like it is twenty degrees warmer than the actual temperature.
The
20 Degree Rule is just a rule of thumb that can differ from person to person, but overall the logic is the same regardless:
Many outdoor activities are aerobic ones.You will be generating body heat and will soon warm up. If you start off the trip and you are slightly cool, you are probably dressed correctly. When you stop, you can always throw on an extra layer. If you overdressed, you will be soaked in sweat and will be cold quite quickly when you stop.
I find a light hat (fleece or wool) is an excellent way to regulate the body temps in cold weather. Take off if hot; put on if cold.
FWIW, I was hiking the other day in town in very low temps (less than 5? 0?) and slightly windy conditions. I had on a polypro top and bottom. Montbell rain pants, a lt fleece hat, gloves and shell mittens. My lined windshirt was stowed in a fanny pack.
On the up hills, I was very warm to the point I had to take off my hat. On the downhills, I had to throw on my hat again along with a windshirt. On the flats, I took off the jacket again. I tend to hike consistently. Alas, I am very thin on my head, too.
(Hence the almost constant need for head covering...)
Overall, I get my bottom half just about right for the general conditions, and layer on my torso, head and hands as appropriate
This holds true (along with the 20F rule of thumb) for my outdoor activities whether hiking or skiing/snowshoeing in all four seasons (well, I don't ski in the summer.
)
As a side note, for winter use, when I am more concerned about warmth than weight (and I am wearing most of my layers), I tend to favor wool base layers (except for the liner socks) as it is more forgiving of sweating I find. A wool hat tends to be warmer if it gets damp in snow vs a fleece hat as well. A surplus wool sweater is now my warm layer of choice, too. In the cold, dry conditions of Colorado, I find wool works very well overall.
In three season backpacking, when weight and bulk is a chief a concern (and most of my layers are stowed), I tend to wear synthetics. Any moisture in spring through fall tends to be rain (or very wet snow), so the quick drying properties of synthetics comes in handy.
Overall, you may find one combo works better than another based on your budget, availability of what you may already have or just personal preference.