乌云密布

The morning began fine, but now clouds are banking up.

早晨开始是晴天, 可是现在乌云。

The sky clouded over before the storm.

暴雨来临前, 天空乌云。

The sky clouded over; we could see there was going to be rainstorm.

"天空乌云,们看得出来暴雨了。"

The sky blackened and soon it began to rain.

天空乌云, 便下起雨来。

The thick clouds passed overhead, but fortunately the rain kept off the whole day.

虽然乌云, 但幸运地一整天都没下雨。