There's no doubt that both extremes are equally miserable. I dont see how someone can successfully prospect in miserable heat, or freezing cold.I would like the problem of 95 degree weather, but the question works the same way in reverse. In Maine I remember commenting on the weather being 13 below zero, now more people might be willing to let you in to be polite and to get out of the cold themselves but actually walking around for a while in that weather does not sound fun.
50 degrees would be the perfect canvassing weather for me.