If you are ever outdoors you should realize that the only thing between you and the elements is your clothing, and your clothing counts, so what you wear is everything. In any climate hot or cold layering is always key, wearing light layers in the summer, and thicker layers in the winter. The types of fabric you layer with also factor greatly, such as light cotton in t-shirts versus heavyweight cotton as in flannel, in the winter the main fabric you want to focus on for warmth is wool, if you need to keep warm in any situation wool is the way to go. wool keeps its warming ability when it wet, which if you are outdoors, camping, hiking, at some point you will get wet.
Even if you plan on going camping or prepare for a shtf in the summer time, and you are updating your BOB for the summer, remember that it does still get cold and chilly at night. My main camping style is in a hammock going light weight, and in a hammock you always get a breeze running up the bottom.
my information here is expanded on in many books, from writers who had editors and threw much more into their work. I am having a hard time as of late staying focused on this blog. this tidbit of information was pulled from but not word for word or any lack of knowledge of my own, from Les Stroud in his survivor man shows and his book Survive.