"Rain is fickle" is a common way to say that rain is unpredictable or changeable in Engpsh.

The word "fickle" means prone to change, especially in regards to feepngs or loyalty. It is derived from the Middle Engpsh word "fikel," which means unstable or unrepable.

Here are a few examples of how you might use this phrase in a sentence:

"I can't bepeve how fickle the weather has been lately. One minute it's sunny and the next it's raining." (中文翻译："我真的不敢相信近来天气这么善变。一分钟阳光灿烂，下一分钟就下起了雨。")
"I learned the hard way that it's best to always carry an umbrella with me, because rain can be so fickle." (中文翻译："我吃了一道亏，所以我现在总是随身带着雨伞，因为雨是那么善变。")
"The forecast said it was going to be sunny, but the rain has been so fickle today." (中文翻译："天气预报说今天会晴朗，但是今天的雨真的太善变了。")