********** This section is still under construction and is being revised and expanded **********
Clothing is your first line of defense against the elements. Use a layered approach when selecting clothing for outdoor activities, emergency preparedness, or travel. Fabric type is critical for function and comfort of each clothing layer.
In hot climates wear loose fitting clothes that wick moisture away from your body. Cotton, linen, and silk work well in hot weather. I personally wear a silk shirt for warm weather hiking. Silk seems to wick sweat away almost immediately. New silk shirts can easily cost $50 or more but I found silk aloha shirts for $10 or less at local thrift stores.
Cotton can kill and denim restricts movement, retains water, dries slowly, and is heavy. In bad weather cotton is NOT your friend. Heavy cotton is durable, good for work, fashionable or going out on the town but generally NOT good for outdoor and trail use.
For cold weather wool and synthetics wick moisture and provide insulation. Down works very well when dry but loses ALL insulating ability if wet. A down jacket with waterproof shell is a good option for warmth. Jackets with synthetic insulation are heavier, bulkier, but more effective if wet (details).
Wool is an excellent fabric. It is heat and flame resistant, can be an effective wind barrier, often contains lanolin which makes it water resistant, and it wicks moisture. When exposed to high temperatures or sparks wool will not melt like synthetic fabrics. Wool is an especially good material for socks because of its wicking properties and durability.
For socks always use wool. Wool socks wick moisture away from your feet and are more durable than synthetic socks. You should always carry at least two pairs of socks and rotate the socks periodically. Hang the wet socks on the outside of your pack in warmer weather so that they can dry.
In cold weather use a layer of silk, polyester, or wool. These provide warmth and wick moisture away from your body. An insulating layer goes over the wicking layer. A waterproof shell layer then goes over the insulating layer. The outer shell should be waterproof and breathable. If the outer layer is not breathable then it should be loose enough to allow for some airflow. Jackets should be at least hip length. Plastic shells such as ponchos can be used if nothing else is available. The goal of the outer layer is to keep the inner layers dry.
Light gray works well for blending into urban environments. Bright colors are good when hiking because they are more visible and easier to see if you get lost.