The weather in Tibet can change at any moment. The key to being properly dressed while trekking in Tibet is layering your clothes. The reason layering is so effective for trekking is that your body temperature varies based on your own tolerance to cold and heat, the difficulty of the trek, and weather conditions. I am giving a very basic approach to layering dividing layering into three categories.
Base Layers (moisture and heat management
The first component of the base layer is a light weight layer designed to fit snuggly against the body. You want to make sure your base layers are made of a material that has wicking properties. As you sweat it’s important that the moisture is pulled away from your body and evaporated. The two best options are synthetic materials such as polypropelene or capilene, or go natural with wool. Merino wool is my favorite as it doesn’t smell like synthetics tend to after a few days of building up that good funky trekking aroma! Smartwool is my favorite brand.
Mid-Layers are meant to provide additional insulation to the body. A mid-layer can be a fleece or wool sweater. Fleece is nice because it is very light weight, but can tend to not breath as well as a wool layer. Many companies are combining synthetic and wool blends to give you the best of both worlds. I also like to use a fleece vest as it keeps my core warm while adding great breathability from my free arms.
The main purpose of the outer-layer is to protect your body from the elements robbing it of heat. A fleece windstopper jacket or soft shell jacket are great for light moisture and windy conditions. I love soft shells for their versatility to cut wind and light rain while maintaining more breathability than a fully waterproof shell. A waterproof shell is a must in case of rain or wet snow. When purchasing a shell make sure the seams are taped. Gore-tex is the most famous of the waterproof systems, but many companies offer cheaper alternatives that work just as good such as The North Face’s Hyvent system. In extremely cold conditions a down jacket provides the greatest amount of warmth. I have found for myself that when I am not moving, and sitting around camp I love a down jacket for warmth, and they double very well for a pillow.
The best gear for you is what fits you best. Many people, myself included, have made the mistake of purchasing gear based on a brand name without checking the fit and feel for your individual body.
I most familiar with the North American gear scene. REI in the USA and MEC in Canada are my two favorite brick and mortar stores to go and try stuff on. I do most of my shopping online by watching for deals to be had. Used gear is also a great cost effective option. The REI garage sale can have some stellar gear for very good prices. Craigslist is also a great place to shop.
Here are a few of my favorite sites:
Buying knock-off brands in Asia can be a much cheaper way to obtain necessary clothing. There are many suitable fleece sweaters and jackets for sale. When purchasing waterproof shells be very careful I have seen many coats that looked very good fail to perform in wet conditions. China has some good national brands that can be cheaper than the Western brands. I have found that you will not have the same great fit you get from the American brands I am used too, but they perform well in keeping you warm and dry.