Let me put it this way. As a sniper i move from vantage point to vantage point, rain covers my footsteps when i'm sprinting from place to place. it also masks my shots so its harder to grasp my position. Lastly its easier for me to see players through the rain with a scope than it is for them with sights and normal vision.
Therefore during rain the combat dynamic changes for certain styles. Which is a good tactical game mechanic. Therefore i voted to keep rain.
Thanks,
Dan