a bolt from the blue

Something completely unexpected or surprising; that which occurs without any warning. We always thought of Michael as a lifelong bachelor, so it was a bolt from the blue when he returned from his vacation sporting a wedding ring! News that they were going to dissolve our company came like a bolt from the blue. We're all still in shock from it. We all thought Grandma was healthy as can be, so her cancer diagnosis came like a bolt from the blue.

a bolt out of the blue

Something completely unexpected or surprising; that which occurs without any warning. We always thought of Michael as a life-long bachelor, so it was a bolt out of the blue when he returned from his vacation sporting a wedding ring! News that they were going to dissolve our company came like a bolt out of the blue. We're all still in shock from it. We all thought Grandma was healthy as can be, so her cancer diagnosis came like a bolt out of the blue.