Is there a way to adjust the weather to be..... more?  Not asking about rain.  100% Clouds is just not enough.  I want dark-dark skies during the day.  Other than changing my graphics settings, is this possible?

Have you tried the Realistic Weather plugin?

Yes, but even at 100% clouds, it's still pretty bright.  You'd think that adding complete cloudcover would change the brightness of the whole scene, but it does not.

did u try 100% clouds and 100% fog ? i find this atmosphere through days nice.
other whay maybe request a plugin where u get a dark brightness all over the screen and simulate it.