I'm going to disagree, at least for me personally, I don't find nylon trekking pants to be all that warm on their own. They're not the most packable thing, but I still have a pair of jeans with me.

If you're camping down into the 30s, I imagine you probably are going to want a pair of long underwear anyhow, I did those with jeans in Iceland and stayed nice and comfortable in the low 30s.