If the sky is cloudless, there are no clouds in it.
英漢詞典釋義
adj.
無云的,晴朗的
The sky is quite blue and cloudless.蔚藍的天空晴朗無云。The sun shone on for hours in a cloudless sky.天放晴了幾個小時。It was the first of August,a perfect day,with a burning sun and a cloudless sky.八月一日這天,陽光普照,萬里無云。