I guess how cold will depend on what part (as in how far north) of Alberta you are talking about. The farther north you go usually equals colder temps. As for where to buy, I am just guessing here, but I would suspect that buying once you get there would be the best, local stores probably know what works best for their area. Plus you don't have the hassle of shiping. On the other hand, by Sept the stores might have already sold most of the good stuff. Decisions decisions.

Have fun!!!