We use this expression to say something happened as a complete surprise.
You can use this phrase in ………… language.
Spoken
Written
Formal
Informal
Example 1
A: Did you know Honza was coming to visit us?
B: No, he just telephoned out of the blue. It was a complete surprise.
Example 2
A: He’s still in shock about winning the first price!
B: Yes, it came out of the blue.