Absolutely necessary for deploying any smoke mortars. When smoke mortars are deployed, they're deployed well remote and out of view of operations area, and trying to judge wind direction travel of the smoke is impossible. (An idea, toss a smoke grenade nearby and watch the smoke, and make some assumptions of wind within the operations area.)
Unsure if wind currently affects flare mortars.
Unsure if wind currently effects flight dynamics.
Wind does currently affect bullet trajectory?
The only weather reporting I have seen on multiplayer servers is maybe on the entry screen or the groups screen, or maybe one a server restart?