come out of a clear blue sky
come out of a/the clear blue sky
To happen unexpectedly. She seemed so surprised by the news that it must have come out of a clear blue sky. You need to work hard—opportunities don't just come out of the clear blue sky.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
come out of a clear blue skyand come out of the clear blue sky; come out of the blue
suddenly; without warning. Then, out of a clear blue sky, he told me he was leaving. My sister Mary appeared on my doorstep out of the blue, after years with no word from her.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.