Most of the winter rock in the States lies in desert regions; i.e. the good days are awesome but the nights are invariably a bit crisp. The best locales have micro climates. Indian Creek is a great example; I was once obsessed with a project there and sitting in the car watching it rain with two partners who wanted to bail for town immediately, "You guys better hope it doesn't start snowing because as soon as the first flakes fall we're walking up there and you two are belaying and spotting [the run-out hard start]." It snowed, I sent.