I'll admit, I'm not completely certain about what the winters will be like. As you said, it's rather warm for this season, but that doesn't necessarily rule out the possibility that it will be cold later. I can only hope that it isn't; I can only imagine that traveling on the routes in the cold is an absolute nightmare.

As for your other question... I've only fought one gym leader so far, admittedly, but he wasn't much of a challenge at all. I've been told that it's more entertaining if you put limits on yourself during the battles and that they do get harder, but from what I've seen they're not particularly inspiring.