out of a blue sky

out of a blue sky

Completely unexpectedly; out of nowhere. A variant of the more common phrases "out of the blue" and "out of the clear blue sky." She seemed so surprised by the news that it must have come out of a blue sky. I was just about to give up hope when, out of a blue sky, an old acquaintance from college called me up with a job offer.
See also: blue, of, out, sky
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.