noun
fickle weather; unpredictable weather
Describes weather that changes suddenly and unpredictably, often with a nuance of being erratic or crazy. The term 気違い (crazy) is now considered a discriminatory word, so this compound may be avoided in polite contexts.
今日は気違い日和で、晴れたと思ったら急に雨が降り出した。
Today's weather is fickle; just when I thought it was sunny, it suddenly started raining.
A more neutral and common expression for changeable weather, without the potentially offensive nuance of 気違い.
Compound of 気違い (crazy, mad) and 日和 (weather, fine weather). The exact origin is uncertain, but it likely arose as a colloquial metaphor for weather that seems to act crazily.