I just got my first chickens since I was a kid, and am trying to raise them at high altitude in the Rockies, so extreme cold(-20 to -30 at times) is an issue..
We get pretty cold winters here too. There is a thread about winterizing for newbies, you can search for it in the Raising Backyard Chickens section of the Forum.
some people stack hay 2-3 bales high around the perimeter of the run to block wind. If your coop is draft free and has ventilation panels high up, your birds should be okay. Some of your flock may decide not to set a foot outdoors in bad weather, so they will pretty much determine how much winter they want to deal with.