Definition of "out of the blue" []

• Unexpectedly; without warning or preparation (adverb)

Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License

• "One dad, Andrew, told me that out of the blue his son Lucas began doing Lampa."
• "Impacted as he is by the concept of a budget, he decides out of the blue that his family needs a budget."
• "Then out of the blue she sent a note with Willy Insell that she could not see him for some time—but she gave no reason."