My normal carry is IWB, which is not the most accessible under multiple layers during the Midwest winters. * * *
I like to carry either AIWB or closer to 1:30-2 year round. That means that even in real cold weather it is not terribly difficult to reach my firearm. As long as I'm not wearing a parka. Heavy gloves are more of an impediment IMO.
Even when I lived up in AK I found that a Carhartt jacket and thermal sweatshirt were good for everyday use. Hunting on the tundra, I did use a shoulder rig as reaching my belt under the parka and coveralls was pretty much impossible.