Really enjoyable addition, however it would be nice if we could cycle the weather if it turns out to be a hindrance for the situation (IE too dark, blocking/blurring view of something).
I'd also like to suggest adding a way to adjust the volume of the rain separate from other audio, & an option to adjust rain thickness would be nice imo. (& maybe weird suggestions but stuff like snow, leaves, tornado, or flower petals would maybe be neat little optional effects to add too.)
It'd be funny if there was an option to increase the odds of getting struck by lightning & the rate of lightning strikes for a bit of a group challenge run lol (maybe make it have the LoZ BoTW weapon rain zap effect before you are about to be struck, & make the counter to it crouching for a moment or moving under something to stop it from striking you).
You can turn down the rain volume in the sound setting using the environment slider. Changing the sound of the rain specifically would require me changing how the rain sound works.
I can add settings to change rain 'quality' and as for other effects like snow or leaves there may be a future mod that contains those things...
Your lightning suggestion has been noted.