The thunder roars loudly, but little rain falls. 或者说：All we hear is thunder, but no rain falls.
虽然这样直译比较容易理解，但是老外的说法是这样的：
Actions speak louder than words. (行动胜于言谈)
或All we hear is words, but there is no action. （只动嘴不动手）
或Actions and words should go hand in hand. (言行必须一致)
另外，还有英语里还有这样的说法：
An empty barrel makes biggest sound.（空洞的话说得太多了。）