it never rains but it pour 字面意思是“不雨则已，雨则倾盆”，用来比喻“不鸣则已一鸣惊人”或“祸不单行”。

【例句】
I really feel sorry for Mike. First his wife left him. Next he lost his job. Then somebody stole his car. Like they say, it never rains but it pours.
我真是为迈克感到难受。先是他的太太把他扔了，然后，他又丢了工作，接着，他的车又被人偷了。这真是像人们所说的，祸不单行呀。

My wife is ill in hospital and I have sprained my ankle. It never rains but it pours.
我的妻子生病住院，我有扭伤了脚。真是祸不单行。