If you live in the north and have a lot of experience hiking you already use layers to keep yourself warm and comfortable. If you do not usually hike in colder weather, or are new to hiking all together, then you need to know about dressing in layers. You don’t have to dress like the abominable snow man to stay warm during cold weather hiking and camping. If you are going to be standing around on snow or ice with little activity for extended periods of time, then you will want to layer on thick long underwear and parkas, as well as insulated heavy boots. While hiking however, your body will warm up nicely and you will find that a heavy single layer or two will not work.
When I am hiking in cold weather, I wear the following layers: First, a base layer that consists of a thin polyester pull-over. As temperatures drop I will replace the polyester with a thin Moreno wool long underwear top, and if it is really cold, I wear a medium weight polypropylene long underwear shirt. Even in very cold weather though, I have regretted choosing the heavier top as I warm up very quickly in it. I like to have it with me in a pack however, if I am going to be spending time standing around in camp for its extra insulation. On top of this base layer I wear a fleece full-zip jacket. Mine zips up high enough to act as a neck gaiter as well. This layer is the first to come off when I warm up. If there is no wind or precipitation, I will sometimes wear it as my top layer, as it more readily wicks moisture for quickly cooling down. Over this I wear a Goretex wind/rain shell. This combination of layers works well for me in temperatures down to about zero degrees and would work well below zero with moderate exercise. On a recent hike with temperatures hovering around -10F I had to remove the fleece and unzip the pit-zips of the Goretex, as well as zipping the front zipper halfway down. This was easily reversed to conserve heat when I stopped for any length of time.
For my legs, in very cold weather, I wear a lightweight pair of Moreno wool long underwear pants, under a pair of medium weight convertible polyester hiking pants. This usually keeps me comfortable throughout the hike. The wool keeps my lower-half almost over-heating, resulting in the need to add or remove the fleece or shell to keep from sweating too heavily. For my extremities I do the following: On my head, I wear a wool ski cap which I often remove to regulate heat. Most of your body heat is lost through the top of your head, so this is often all you need to do to keep your body heat regulated. Once I am moving my hands stay pretty warm with only a medium weight pair of fleece gloves. Your experience here may be quite different as there is great variability in how cold effects different people’s hands and feet. My wife for example needs a thick set of mittens in temperatures below 15F. She keeps these on even when expending a good deal of energy, for instance snowshoeing, when I may remove gloves altogether. I always carry chemical hand and toe warmers to provide extra warmth when needed. In very cold weather I always start with toe warmers as my boots are not insulated.
If you are going to be standing around in an overnight camp, or at the terminus of your hike while you eat lunch, you may want to carry a down jacket to replace the shell. If you have been properly adding and removing layers this may not be necessary. Usually the need for additional layers when you stop, if you are wearing the setup I describe, is related to having begun to sweat too much resulting in rapid cooling when you stop. Sweating can be regulated in two ways: By removing layers and by slowing down your pace. It is really critical not to sweat heavily when out in very cold weather. If you are going to keep from cooling too rapidly, or even becoming hypothermic when you stop, you cannot sweat heavily and wet your clothing layers. Proper temperature regulation should trump speed to destination. In very cold weather when backpacking I do carry medium weight polypropylene tops and bottoms and a down jacket for wearing around camp. Also, a warmer pair of gloves is needed if I am going to be standing around.
Experimentation is the best way to find out what works best for you. You should do this, to start, on short hiking trips where you are reasonably sure to return the same day (although you should be prepared for an emergency overnight stay). Carry a daypack even on a short hike, so that you can bring a few alternative pieces of clothing to try as you hike. This way when you go on longer or overnight hikes you will be prepared to be comfortable no matter how cold it gets, or how much effort you have expended while hiking.
Another consideration whenever temperatures are cold is the effect of wind and precipitation. In cold weather precipitation comes in the form of sleet or snow. These can be fended off nicely with a rain shell and pants. But don’t forget that wind can be an even bigger problem with low temperatures. Here again a rain/wind shell and pants are critical and should be brought with you whenever you are out in the cold. Another addition for very cold temperatures is a good synthetic balaclava and for blowing snow a pair of ski goggles. One other point that should have been stated first: NEVER layer in cotton clothes! Cotton absorbs moisture and takes forever to dry. In cold weather consider cotton “death cloth.” Never wear it and that includes cotton blue jeans. Actually, don’t even wear cotton in the summer, but that is another post.
Winter hiking is great, and you certainly don’t have to be uncomfortably cold while participating. Take a few precautions and dress in layers and you are sure to have a great experience.