This depends on your individual needs, but our advice is to take warm, windproof, waterproof clothes that you can easily add or remove in layers. Multiple layers of medium-warmth clothing provide more insulation than single heavier articles. This is due to warm air getting trapped between the layers and acting as further insulation. Look for clothing made of wool, silk, and new synthetic fibers, all of which retain heat better than other materials.
Layers give you the flexibility to control your temperature. The most important layer is the outer waterproof and windproof shell. More information about this can be found in our expedition manual, which you will receive at time of booking.