back on the .COM (angelic opera noises, accompanied by trumpets heralding news from a glorious land now passed), forum giljay verified that the battles fought in a single turn/year are by season. Thus 4th, (and subsequent), battles are winter wonderlands.

I'd cite the post, but uh, well yes. From the words of good ol' gil, straight to you., sorta... secondhand kinda... well, just trust me.