I remember when we shot IMHSA handgun silhouette and several of us were shooting .44 magnums with cast, gas-checked SWC bullets. A spotter behind the shooter with a 36x spotting scope could see bullets going to the 200 meter rams when the sun was behind us. He could also see the bullets hitting raindrops, (or having the shock wave hit them) in a heavy rainstorm. There didn't appear to be any measurable effect on the bullets from the rain, but we didn't shoot especially accurately, say, 2 MOA.
If I can't be with the rifle I love, I love the rifle I'm with!!