Snow and below freezing temps, or sunshine and t-shirt weather - conditions for your ski tour can change a lot from the bottom to the top in very little time. You will also sweat a bit on demanding climbs, then quickly find a chill on the downhill – there is no constant temperature on a ski tour!
To be well-equipped for various conditions, you need to focus on the materials of your layers and dress yourself appropriately.
The base layer, which is next-to-skin, should have a performance property that ideally regulates your body temperature, wicks away sweat, and at the same time ensures that you do not overheat. Worn over your baselayer, is your midlayer, which should be a warm, insulating jacket that you can put on and take off easily. The last layer you need is an outer layer, which is either a softshell or hardshell jacket or pant to protect you from wind or any other types weather.