You look to the north, and see a perfectly innocent looking cloud formation. Ah, pretty. Everything's normal. Except for that odd glow. You turn to south/southwest.
Oh, that is what is creating the odd glow. This sky is taking over the normal sky.
This sky is creeping ever closer, obscuring the blue. Like in a bad sci-fi/disaster film, I can almost see the shot of the worried townsfolk all looking at the sky in wonder. Or horror.
I don't get out much.