The sky was overcast.

天色灰蒙蒙的。

《新英汉大辞典》

The sky was overcast, the ligtning leaped from cloud to cloud.

天空乌云密布， 电光在云块间闪动。

《新英汉大辞典》

Time passed slowly. The sky was overcast. Autumn rain lashed the windows. At times, the empty bed seemed, I thought, to resemble a grave. I felt afraid.

时间慢慢在流逝，天空布满了乌云，一阵秋雨抽打着玻璃窗，有时空荡荡的床铺看上去犹如一座坟墓，我害怕起来了。

youdao

Washington had warmed up, the swift storm of the previous day had passed, the sky was overcast but the air wasn't painful in a wind-chill way, and the capital was full of men in cowboy hats and women in long furs.

WSJ: Way Too Much God