I flew through fog this week, only noticed the moisture covering the drone after landing. I wiped it down, removed the battery, and let it air dry on my desk. No issues. I'll probably avoid it if I can in the future.
I fly my mavic pro platinum in the rain for about 15-20 minutes often with no problems. I wipe it down take the battery out and leave it near a fan. I fly in fog/clouds regularly with the MPP & M2P in Maui with nothing more than some moisture on it with no problems either. When its humid out i don't notice any problems either