Yeah, you always start in the northern hemisphere. If you didn't touch any of the world size settings then the pole-equator distance is 100,000 blocks meaning you've got a good bit of walking to do to get to some of the hotter biomes. Hopefully you'll get lucky and find a few translocators or something to help you travel. You don't need to go all the way down to the equator to find deserts and the like, but you will need to go a significant distance, probably at least 25,000 blocks or so.