Depending on where you live, there will almost always be below freezing at some point during the year. In order to stay warm, you can’t just wear normal clothing. You have to “layer up” in order to stay warm. Four layers is the most reasonable amount for many cold climates, although when it is warmer you can take off one or two of your outer layers. The base layer is the one closest to your skin, and is generally the best material for this is polyester. The mid layer is the next one out, serving mostly to add a little bit of warmth without increasing the bulk of your garments. The best material for this layer is probably nylon. If it is really cold, you will also have an insulating layer, designed to increase your warmth a lot, while also sacrificing some space. Polar fleece or pile fleece are probably the best materials for this layer. Finally, you have your outerwear, or shell. This keeps the outside weather off of you, and generally you want to aim for water resistant shells to keep snow and ice from getting into the insulating layer. A thicker jacket is probably best for this layer. Overall, layers are very important to stay warm in cold climates, and it is very good to bundle up.