They woke to a clear blue sky.

他们醒来时天空碧蓝。

《牛津词典》

The sun was radiant in a clear blue sky.

湛蓝的天空阳光灿烂。

《牛津词典》

The sun blazed down from a clear blue sky.

耀眼的阳光从清澈蔚蓝的天空中照射下来。

《牛津词典》

And one day, outof the blue clear sky, I got a letter from Jenny wondering if I couldcome down to Savannah and see her, and that'swhat I'm doing here.

VOA: standard.other

The sky was just a little lighter blue than his suit, clear and even with only one cloud in it, a large, blinding white one with curls and a beard." Notice that image of the cloud, the blinding white cloud.

天空比他身上蓝色的西装颜色更亮，更清朗，甚至,空中只有一朵白云，是大而亮白的螺旋状和,胡须状，注意这多云的图像，一朵亮白的云。

耶鲁公开课 - 1945年后的美国小说课程节选

You know that feeling on a clear blue sky day.

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It was a day like this one -- a clear blue sky, but a sky that would soon be filled with clouds of smoke and prayers of a nation shaken to its core.

WHITEHOUSE: President Obama Speaks at a Pentagon Memorial Service in Remembrance of 9/11 | The White House

"Fearful of the outcome, King Angus led prayers for deliverance and was rewarded by seeing a cloud formation of a white Saltire - the diagonal cross against which Saint Andrew had been martyred - against a clear blue sky, " writes Mr Reid.

BBC: Saltire