Loss of heat in the back country can lead to a lot of problems.
The joys of solitude of the backcountry also mean you have to be more vigilant about what you wear, eat, drink and be proactive to prevent problems before they happen.
Why is this such an issue? Water has 70 times the convective heat transfer of air, which is how it cools you in the summer and why you want to avoid wearing it in the winter.
Wear the right clothes. We discussed cotton socks, but before you go out you need to think of shoes, shirts, pants, underwear and waterproof gear (and sealing wax and kings…) -everything you need close to the body.
Shoes for the backcountry deserve a lot more space, so we will cover them in greater detail.
Cotton holds water very well so is not an ideal fabric for the backcountry. I still like to have one cotton t-shirt on trips that I expect good weather because I find them comfortable and useful in many ways.
That said mostly I travel with wool and synthetic fabrics. Aside from being light and packing small, these fabrics hold heat when wet and dry quickly.
For warmer weather I have an old pair of pants from Patagonia that were made for climbing. They dry quickly, have nice stretch (for climbing or interesting terrain) and have a pocket on the thigh that allows a snack when you are hiking or on a ridge. In winter I use a pair that is designed for skiing – wind proof panels and zips on the ankles to go over boots.
For the body I have some nylon t-shirts for underlayers and varying weights of wool base layers. I take a small collection – usually two light shirts and two weights of base layers. You can easily stack them up for extra warmth and also wash one and hang it on the back of your pack to dry it for the next day.
Staying dry and warm in the backcountry requires good planning, but will keep you from having to deal with far greater issues like hypothermia.