clear as day; patently obvious
Idiomatic expression emphasizing that something is extremely obvious, often used for negative situations or consequences. The literal image is 'clearer than watching a fire'.
See also: 火を見るより明らか
It's as clear as day that he is lying.
このままでは失敗するのは火を見るよりも明らかだった。
It was patently obvious that things would fail if they continued like this.
A set phrase of uncertain origin, literally meaning 'clearer than watching a fire'. The comparison to fire suggests something so obvious that it is as unmistakable as seeing flames.