To have a face like thunder:
脸像打雷一样 ×
火冒三丈 √
例句:
He had a face like thunder when he came out of the manager's office this morning.
他今天早上从经理办公室出来的时候满脸怒气。
To chase the rainbows:
追逐彩虹 ×
痴人说梦 √
例句:
You have only started two months ago, you are already thinking about promotion. Well, I think you're just chasing rainbows.
你才来了两个月就想着升职的事情了,我看啊,你是净想好事儿呢。
Rainy day:
① 雨天
② 穷困时期 √
例句:
I'll put the rest in the bank for a rainy day.
我要把余款存入银行以备不时之需。
(内容来自学英语口语,如有侵权请联系删除)