Already particles were beginning to fill the inside of the car, making a gray fog that rapidly darkened.

The sky was darkening rapidly, for the sun had long ago sunk below a blazing horizon.

The short Martian twilight started upon its rapidly darkening career.

The closing image, of a man moving across a rapidly darkening stage, is quietly stunning.

Finally, they broke through the cloud cover and emerged into a rapidly darkening, clear sky.

The day darkened rapidly, as if God had applied a heavy finger to a celestial rheostat.

The sky was darkening rapidly and Lenstrom's face clouded with it.

Jonathan looked up at the rapidly darkening sky and felt a speck of rain.

As they sparred, the sky was darkening rapidly above them.

The evening sky was rapidly darkening around them.