Non-Epic Game: It is the hight of summer, the last two sessions were spent underground in a cave. The 3-4 sessions before that they were in a small, but thick, coniferous forest.
Epic Game: They are in the middle of the ocean on a ship, they are about to dive down to the bottom so.. aquatic to say the least
I'm guessing the default climate is temperate? My group is in a forest right now; they'll be moving to the Underdark shortly and then into the mountains.
Other: having just assaulted a mind-flayer city-ship in space, they're now returning in their own starship to the main body of the Galactic Federation. (And yes, this is a D&D-based group.)