out of the blue

Short for out of the blue sky, likening an unexpected event to lightning or rain coming suddenly from a cloudless sky.

• "After I hadn’t heard from her in six months, she called me out of the blue to meet for lunch."
• "I really can't understand how something like this could simply pop up out of the blue."
• "I deckhanded on a fish boat for four years and knew no fisherman likes to be called out of the blue and have his numbers demanded!"
• "Just as it appeared Arsenal had taken the sting out of the tie, Johnson produced a moment of outrageous quality, thundering a bullet of a left foot shot out of the blue and into the top left-hand corner of Wojciech Szczesny's net with the Pole grasping at thin air."

• bolt from the blue
• just like that
• next thing one knows
• out of nowhere
• thin air