There is a lot of information about “The Layering System”. The basic idea is that you have multiple layers of clothes on you, so you can take clothes of when it’s getting hot, or add a layer when it’s getting colder. Most layer systems will have a 3 layer system, but IMHO 4 layers are better for my trip.
So why you may ask? I’m planning to go to Scandinavia in the summer and yes, in the summer the temperature is very nice in Scandinavia. My plans are to stay in Scandinavia until it’s too cold for me! And for now, I don’t know exactly what will be too cold, I know I don’t mind when it will be freezing a bit.
So in my trip I will go from nice weather, 25 degrees in the summer until like -5 in the autumn. I think 3 layers isn’t flexible enough. The first layer, the base layer will be a longsleeve Merino wool from Icebreaker. Recently I bought it in a sale with 40 percent off, these things are expensive but I think (at least in sale) it’s worth the money.
The second layer will be some sort of fleece vest. I haven’t got this one yet but when it’s used when it will get a bit colder in the summer evenings. The third layer is an important layer for when it is getting colder, the insulative layer. This will keep the cold air out and it will protect (to a certain point) to the elements. For this I’ve bought a synthetic jacket from Salomon, the Drifter.
So why not a down jacket? Well, when the jacket will get wet it will be hell to dry a down jacket. A synthetic jacket will dry out a lot quicker. The fourth layer is the hardshell. I hope I don’t have to use this layer a lot, but when the weather get’s really bad a hardshell jacket will save your ass.