Quite honestly I do not think you should take too seriously breed descriptions that include 'winter hardy' or 'cold tolerant', because it is such a vague general thing and depends on exactly what the writer means and what your winter conditions are like.
Certainly there are some breeds that are notably *less* cold-tolerant or winter-hardy -- things with really giant combs/wattles like Andalusians, or long thin comb points like Buttercups, or body-size issues like Seramas.
But other than that, it is really really not clear to me, from hearing peoples' experiences with different breeds in different climates, that there is any particularly predictable relationship between breed and winter weather other than the obvious fact that single-comb breeds are more prone to frostbite than those with smaller tighter comb types, and breeds with very little in the way of combs/wattles (chantecler, buckeye) are the least frostbite-prone of all.
As far as "how cold is Cold for a chicken?" it depends significantly on your humidity. I don't know what part of the PNW you are in, but if it is one of the sort of Seattley type parts, 30 F and chronically 98% humidity can be a real frostbite risk; in dry air, though, chickens are typically fine down to much lower temperatures, approaching 0 F or even below. This assumes a draft-free environment and ample food, of course.
Good luck, have fun,
Pat