Clouds drifted across the sky.

朵朵浮云在空中飘过。

《牛津词典》

The dark clouds in the sky meant that a storm was coming.

天空中的乌云预示暴风雨即将来临。

《牛津词典》

The clouds had spread and covered the entire sky.

乌云铺开，遮蔽了整个天空。

《柯林斯英汉双解大词典》

They reflect sky, clouds and each other in fractured images and with a shimmering brilliance that has nothing to do with, or any need for, architectural distinction.

WSJ: How Less Became More

It is then that I realise, under an endless sky, with clouds caught mid-scud above me, that the Rizk DBR2 isn't really a car.

BBC: Trick of the light: A California road trip

You remember when you were little and you would keep checking the sky for snow clouds on the offchance that you got a snow day?

FORBES: IRS Won't Delay Tax Season For Sequestration