I probably have a mod conflict going on. Thank you for the help. And the mod. ;-)

I can assure you the mod works as intended, not sure what to suggest to be honest.
The difference between vanilla skies and Sullen skies is quite vast so you should notice it.
Maybe post a screenshot of what your seeing maybe?

It doesn't seem to have any effect.

@jasperloop

All you need to do is subscribe, load the mod, and your good to go.
Are you having problems?

Does this need to be activated somehow or is there a mod which stops it working?

Awesome!

Hey folks, I've added an alternative link for Moschnyi Island since Armaholic has ceased.

Indeed. :-(

rip armaholic