Wait, snow flurries? I don't recall weather effects in the game.
Correct, despite being often requested, COH did not have any sort of dynamic weather. The closest it came was some static effects baked into specific mission maps.
Paragon Chat has an experimental outdoor weather system, the only implemented type so far being snow. The fx for it are 'borrowed' from the holiday temporary snowstorm power, which was just a player-specific effect not everyone could see. As for where and when to find it, well, who can predict the weather really?
As the season progresses I think it's likely that snow will be more common, and by the time the new year rolls around people might be getting sick of it.
If you really want to see it, I hear that it snows more often in King's Row than anywhere else, for reasons. Not a guarantee of course.