If it is warm, I will be wearing a synthetic T-shirt with a very thin long sleeve over it. If it gets cooler, and while I am moving, I will have a thin fleece vest on over that. If it gets cooler in camp, then I pull on my Mont Bell down inner jacket. If it gets cooler than that, I pull on my Western Mountaineering down vest and then the 4-ounce rain jacket. For three seasons, that's all I have with me for layers.