I'll admit that I do very little shooting in the rain.
Today I spent some time at the range shooting from a covered shooting area, through heavy rain, to the target. I noticed that all three rifles we were firing were shooting groups larger than they typically do. All three are .9 to 1.0 MOA rifles every other time they've been to the range. Today they were nearer to 1.5 moa all the time.
Anybody else notice this, or were we just having a bad day?