Funny thing is, ask two people how they feel about the current temperature and you are likely to get a couple different answers. So unless you are saying, "Man, that blizzard outside is harsh." and it's not even snowing, you could probably get away with some comments about it. Like said above, I usually don't mention it unless others do, then I just play along. This kinda goes into that question of, if it's daytime in-game and the RP session lasts three in-game days, then how do you comment on the time of day in RP? Would be cool if we had some kind of temperature gauge in-game, though.
