Maybe because I grew up in the North East, and got tons of experience driving in the snow, that I personally do not think that winter operations are really that big of a deal. Follow the procedures, be smart about taxiing on slippery area's, and give yourself more than enough room. During my CA IOE, I got to fly out of CLT and in the middle of winter operations. I am grateful for that experience, but I really gotta tell you, I think it requires much more thinking, planning, and being on top of your game dodging summer thunderstorms in and around DFW. Especially with fuel loads, and re-routes. You really need to be thinking like a captain to avoid fuel emergencies. ALWAYS contact dispatch if you get a reroute while taxiing to the runway. I'd say that it is much easier to find yourself in a hole with summer flying than in winter flying.
By no means take this as advice on holding off from upgrading. Do what you feel is best for you.