out of a clear blue sky

见 blue

the sky is the limit

(informal)there is practically no limit (to something such as a price that can be charged or the opportunities afforded to someone)

(非正式)实际没任何限制，一切都是可能的

to the skies

very highly; enthusiastically

高昂地；热情地

he wrote to his sister praising Lizzie to the skies.

他写信给他姐妹，把利兹捧上天。

under the open sky

out of doors

露天，室外