Presenting the mean monthly temperatures of Vancouver, Ottawa, and Oxford on the same graph generates an interesting image. Vancouver is basically Oxford plus a couple of degrees in the winter and about five degrees in the summer. Ottawa is much more variable. In the zones where the lines intersect (around April and October), the mean temperatures for all three places are fairly comparable. That may partly explain why I have been finding the weather so pleasant recently.
I wish I had some data that included standard deviations of temperature on a month-by-month basis. I really have no idea which of the three places would have the most intra-month variability, though my suspicion is that it would probably be Ottawa.