Weather does not make sense because there are no clouds. If you haven\'t noticed, precipitation comes from the sky; and there is none in Planeshift.
I think there should be no real holidays, but there should be a holiday where you give a present to all your friends. That would be a really good morale-booster.
That holiday should not be religious so everyone can participate.
But there should be other holidays for religion, that involve rituals or something. Say, on some holiday, people go and hunt in a specific cave for something, and then they eat it. Well, maybe not.
But you get the point.