There are simply just no sounds heard when it's raining. You can hear the wind and other effects during a proper storm but during a regular rainstorm, there's no sound.

Modlist can be found here: https://minecraft.curseforge.com/projects/lurms-realistic-survival/files/2560610

Do you have Dynamic Surrondings? If yes then try to remove it.

I don't have dynamic surroundings, no.

You are super out of date on weather2, update, delete all configs and try again. Working fine for me, noticed you are using tough as nails but its a version that has the seasons stripped out and still working fine for me.

I'm running an old version? I'm using the latest version on Curseforge that I can see: 1.12.1-2.6.9. If that's not the latest, why hasn't it been uploaded to Curseforge?

How about go to video settings > Animations > Rain Splash and then turn it on?
(only if you're using optifine)

Don't have Optifine either. I can see the rain splash animation, it's just not making any sound.

Whatever I read before you edited the post showed an older version, I just tried the modpack, loaded a world, placed down a weather machine, rain has sound, cant reproduce.

I should have mentioned that it's on a dedicated server if that makes any difference. I haven't tested singleplayer since I don't play on singleplayer.