Why is Merry like April weather?

（误译）为什么梅里好像四月天气？
（正译）为什么梅里喜怒无常？

April weather is changeable.
四月的天气（晴雨不定的天气，4月天气，乍雨乍晴）是易变的。

相关表达：

1. blow hot and cold 摇摆不定；喜怒无常

But now you disbelieve me. So you men often blow hot and cold.
可是，现在你又对我心怀疑虑，你们凡人就是这样反复无常啊！

Mary blow hot and cold about her job; every day she changed her mind.
玛丽对于工作的事情拿不定主意，她今天想这样，明天又想那样。

cold blow, hot blow, and gas exhausting in a Clock Hood-type furnace.
本文着重研究钟罩炉内吹扫（排气、冷吹和热吹）三种方式。

2. moodiness n. 喜怒无常；闷闷不乐

Deep and thoughtful, you are prone to moodiness.
深沉，有思想，喜怒无常。

Too much purple, like blue, could result in moodiness.
太多的紫色，如蓝色，可能会导致情绪低落。

Dreaminess, nostalgia, or moodiness may be hard to resist.
迷离、思乡与闷闷不乐变得很难抗拒。

3. moody adj. 喜怒无常的；易怒的；郁郁寡欢的

He relapsed into a moody silence.
他又重新陷于忧郁的沉默中。

This evening Paul had been moody and perverse.
这天晚上保罗怏怏不乐，很反常。

At first I ascribed his long moody silences to depression.
起初，我把他这种长时间寡欢少语归因于情绪低落。