In the novel I am currently writing, the premise hinges on the concept of two parallel universes. The characters manifest differently in each universe--not necessarily opposite, but differently.
As I was plodding/plotting along, one of my characters was trying to orient himself and he mentioned that he did not think they were in a Northern mountain range because it was not cold. That was when I realized that fantasy writers frequently, if not exclusively, write from a Northern-hemisphere perspective. I suppose it may have to do with the fact that high fantasy in particular has its origins in Europe. So, just to twist things up and to emphasize the difference between the universes, I changed the perspective: in one, the further south one goes, the colder it gets; in the other, the further north one goes the colder it becomes.
So now here's the question:
I've never been in the Southern Hemisphere! Does it get colder the further south you get? I know our summer is their winter and vice-versa, but is the weather like a mirror image of the Northern Hemisphere? Geography and science were longer ago than I care to admit.
Also, I was going to have it be summer in both universes simultaneously (they currently are running at the same time-speed), but I was now contemplating the significance of that in light of the new hemisphere concept. If they are on the same time schedule, would Universe 1's summer be Universe 2's winter? I do want to avoid the idea that the Universes are opposites of each other, but this hemisphere concept has intriguing implications.
And then there is the whole problem of flat vs. round world...so many things I have not thought about.
Any helpful suggestions or comments?