Out of the blue means that something happens suddenly with no clear sign that it was about to happen.
The phrase comes from the image of a sudden bolt of lightning appearing from a clear blue sky. Because lightning usually comes with storm clouds, a strike from a blue sky would be very surprising.
The phrase comes from the image of a sudden bolt of lightning appearing from a clear blue sky. Because lightning usually comes with storm clouds, a strike from a blue sky would be very surprising.
Out of the blue, an old friend called him after many years without contact.