"out of the blue" in Chinese (Simplified)
突然毫无预警
Definition
用来形容某件事突然发生，毫无预警或征兆。
Usage Notes (Chinese (Simplified))
属于非正式表达，主要用在描述完全意外的事情上，常与“came”, “happened” 组合使用，比单独用“突然”语气更生动口语化。
Examples
He called me out of the blue last night.
他昨晚**突然**给我打了电话。
A job offer came out of the blue.
工作机会**突然**出现了。
The rain started out of the blue.
雨**突然**下起来了。
She quit her job out of the blue, and nobody saw it coming.
她**突然**辞职了，没人想到。
Out of the blue, my old friend showed up at the door.
**突然**，我老朋友出现在门口。
Sometimes great ideas come out of the blue when you're not even trying.
有时候好主意会在你没想的时候**突然**出现。