I tend to use my ovens all year, but much less frequently in the winter. Not only do I have to wade through snow to get to them, but the ovens take a long time to heat up.
If you're planning to build an outdoor oven and you live in a cold climate, then consider building an oven with not much mass. This would be especially true if you plan on baking mostly flat breads. In other words, just a red or firebrick floor and not more than 4" of mud, earth or brick on the sides and top. You should also totally insulate the oven because it will heat up faster, hold the heat longer, and you'll burn less wood. I will try to take my own advise with I totally rebuild the oven shown.
The photo shows some flat breads struggling to bake.
