bolt from the blue

Something completely unexpected or surprising; that which occurs without any warning. We always thought of Michael as a lifelong bachelor, so it was a bolt from the blue when he returned from his vacation sporting a wedding ring! News that they were going to dissolve our company came like a bolt from the blue. We're all still in shock from it. We all thought Grandma was healthy as can be, so her cancer diagnosis came like a bolt from the blue.

Fig. a sudden surprise. (Alludes to a stroke of lightning from a cloudless sky.) Joe's return to Springfield was a bolt from the blue. The news that Mr. and Mrs. King were getting a divorce struck all their friends as a bolt from the blue.

A sudden, shocking surprise or turn of events.

A sudden, unexpected event, usually of a catastrophic nature. The term refers to a bolt of lightning or thunder that comes from a blue (cloudless) sky and hence is not anticipated. Although “blue” was a poetic allusion to the sky by 1700, the precise expression dates from the early nineteenth century. It appears in Thomas Carlyle’s description of chaotic events of the French Revolution: “Arrestment, sudden really as a bolt out of the blue, has hit strange victims” (1837).