Better sound on rainy days?

I am going to install a fire sprinkler system in my listening room and keep it on when listening to FM on my tuner.

FM tuner reception is clearly better on cloudy days. I have not noted any equivalent weather difference when live-streaming the same signal (often, in various weathers, I A/B the two, analog vs. digital). The "atmospheric conditions" explanation has always seemed true to me. 

Temperatire yes, air pressure and then ionization...

Ionization play a role very important because it affect the body too and not only the diffusion of the waves...

@mitchb I’ll have to admin I do agree! Also, never test drive a car on a rainy day. They drive smoother a quieter. I know that has nothing to do with why our audio systems sound on a rainy day but was the only analogy that came to mind. interesting that you should bring this up. 

Rainy days and Mondays always get me down or so says the Carpenters. Sorry, it just popped into my head.

JD