I've noticed in the most recent screenshot of Old Russia there is snow falling. In the early builds there were no weather effects.
http://www.bungie.net/pubassets/25076/triggerfinger.jpg
There is also snow on the ground in the Beta video on the new Destiny website.
http://cdn.destinythegame.com/video/beta_1080.mp4
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I'd be surprised if there wasn't any weather effects. Old Russia with snow, Venus with rain, and Mars with sandstorms would be gorgeous and add a fun dynamic to the game.