Dark clouds were building over the mountains, and I wouldn't have been surprised if we had snow later that afternoon.

The clouds had been building for days, but had not been expected to break quite yet.

The clouds were building above Los Angeles- and it was a long way to the nearest car.

The clouds build in the late afternoon, and the rain comes at night.

The way those clouds are building in the sky, I ought to drive.

Though clouds had built up the night before, the promise of rain had not come through.

The November afternoon was still sunny, but dark clouds were building over the mountains.

But the clouds were building fast behind them, in the south.

To the east, black clouds were building among the peaks, another cemaros storm.

The way the clouds were building, it was going to be sooner.