Learn English – English equivalent of the Portuguese phrase: “this person’s mood changes according to the moon”


In Portuguese there is an expression that says:

"Essa pessoa é de lua."

Literally "this person's mood changes according to the moon", which means that nobody can predict that person's mood.

Is there an equivalent expression or similar to this in English?

When someone is angry one day and very peaceful the next day…

Best Answer

Such a person is said to be mercurial or capricious.

mercurial: likely to change your mood or opinion unexpectedly

capricious: suddenly and unexpectedly changing your opinion or behaviour without any good reason

An equivalent expression might be, "He/she is as changeable as the weather."