Lovely! And you know me..you don't need a blue sky to have a great sky!
I'm not one for levels too..I know where to find them but horrible at it. I usually go to individual colors I want and boost them up. Don' t know if you can do that in Gimp.
you can do both in GIMP. I've had some fun playing the with curve thingy but not sure if I mastered it yet.