YOU SAID:

Today was a mostly sunny day but at night it became rainy

INTO JAPANESE

今日はおおむね晴れの日でしたが、夜は雨になりました

BACK INTO ENGLISH

It was a sunny day, but it rained at night.

INTO JAPANESE

晴れた日でしたが、夜は雨が降りました。

BACK INTO ENGLISH

It was a sunny day, but it rained at night.