As September has the clear sky and fresh air, it is a very good time to climb the mountain.

由于九月有晴朗的天空和新鲜的空气，这是一个很好的爬山时间。

youdao

The sun was radiant in a clear blue sky.

湛蓝的天空阳光灿烂。

《牛津词典》

The sky was clear and studded with stars.

天空晴朗，繁星点点。

《牛津词典》

The next day the sky was blue and clear.

VOA: special.2009.02.28

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

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

It was a little lake, still and dazzling under the clear sky.

NEWYORKER: Gravel

Thin streams of white smoke fall out of the clear sky onto pastoral farmland, where small fires then dot the landscape and create smoke that blankets the area.

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The baked brown cliffs and the clear blue sky were joined by the tinge of green on the sandstone rocks for the first time, in my memory.

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