Did you know?
Cotton clothing may seem the obvious choice for hiking, but isn't recommended. Cotton, when wet, is a poor insulator, which makes you feel colder and susceptible to hypothermia.
If you're planning a multi-day trek through the wilderness, or even just an epically long day-hike, you will need to carefully consider what to wear. As any seasoned hiker would tell you, jeans and a T-shirt will only get you so far.
Serious hiking requires a more thoughtful approach to clothing, including an accurate assessment of the conditions you'll be encountering, and a thoughtful layering system that will not weigh you down.
Weight is an especially important issue for hikes that extend over multiple days. You can't bring a suitcase filled with half your wardrobe on this type of excursion - you will need to pack very lightly.
Water on our skin traps heat, and when the water evaporates, the heat goes with it. This means that, if you are wet in windy or cold conditions, the evaporating moisture could cool you down faster than your body can expend energy to keep itself warm. It's a recipe for shivering discomfort, and can lead to hypothermia, in extreme conditions.
It is a good thing, as it can help regulate your temperature if it's warm, and can help keep you dry, by letting your perspiration evaporate efficiently. Breathability also means the jacket will be less water-resistant. A waterproof garment or poncho, are not breathable at all, can be waterproof, but that's when moisture on the inside can become a problem.
First, it's uncomfortable. But this is the least-important problem. More importantly, if you are soaked with sweat, you could lose more heat than you need to, leading to chills. In warm conditions, the opposite problem occurs.
The purpose of sweating is to cool your body down, but if the sweat can't evaporate, the heat it contains will stay against your skin, and you could overheat. You'll be producing more perspiration to compensate, which could lead to dehydration.
As is the case in most sports, synthetic fibers like polyester are the best base layers for hikers. Synthetic fibers can be very lightweight, and they absorb very little moisture. A cotton shirt is very absorbent, so it traps wetness against the skin. Synthetic base layers do not have this problem, and are an important part of the equation for staying dry.
Choosing appropriate clothing doesn't necessarily have to be expensive. All you need to do is ensure that you're making the right choice, instead of the easy or uninformed one.