Outside in the street, the sky darkened and rain began to fall.
That day six years ago the sky had darkened too soon; long before night was due.
The sun had set by now and the sky was darkening.
Around them, the sky was darkening with more than the approach of night.
The sky had darkened nearly to black; it Must be near evening, then.
As the sky darkened it was harder to place their feet.
She stood in front of her bedroom window until the sky darkened and the night took hold.
After the sky darkened, the telescope was moved into position.
Now with the air growing cool and the sky darkening, she wanted the experience.
The sky was darkening and the stars were coming out.