bolt from the blue, a

Idioms  

1. Also, a bolt out of the blue. A sudden, unexpected event. For example, Bill's dropping his life insurance was a bolt from the blue for his wife. This metaphoric term alludes to totally unforeseen lightning or thunder from a cloudless (blue) sky. [First half of 1800s]

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Example Sentences

Of “Windermere,” the Oxford literary critic and cultural historian Michèle Mendelssohn writes: “The comedy’s success seemed like a bolt from the blue, a first-timer making a huge hit on his initial outing on the comic stage.”

From Washington Post

Carillion's collapse was for many people a bolt from the blue - a large UK company that had no obvious problems went bust in a little more than a year.

From BBC

Just as she was growing resigned to her loss, the postman rang with a bolt from the blue—a letter from overseas that was signed with her husband’s signature and urged her frantically to disregard any bad news concerning him.

From Literature

The unselfconscious catchiness of “HandClap” was a bolt from the blue – a new way to think about writing.

From Los Angeles Times

But it's a sign of the relative dearth of such performers these days that Crutchfield as Waxahatchee feels like a bit of a bolt from the blue, a splash of freshness amid all the wannabe soul belters and glossy melisma addicts.

From The Guardian