Dress warm - in layers. From what my students and colleagues have been telling me, Kazpat's answer to your post is accurate.
I see you're in Quito, Ecuador (nice city, by the way). Have you ever experienced winter weather?
Astana, Kazakhstan is the second coldest capital in the world, but -20C isn't as bad as it seems as long as there isn't much of a wind (though, from what I'm told, it can get quite windy at times).