The utterance “when hell freezes over” has the same emphatic meaning as “a snow ball’s chance in hell“, in other words, “never”!
Perdition, also known as “hell”, is a hot and firey place. Cold just doesn’t fit in with the place, it will never freeze there.
When someone responds with “when hell freezes over” they are communicating in no uncertain terms that an idea which is being floated will not take place. Or the idea proposed is extremely unlikely to take place or is utterly impossible.
Some might be uncomfortable speaking about hell, and it might not be approprite in certain situations, so another phrase which would works is “not a chance!”
Examples: “Chicago Cubs fans would love to see their team win baseball’s ‘World Series’, but anyone realistic knows the Cubs will win when hell freezes hover.”
“When Christine found out that Darren went out with another girl. ’Will you forgive me?”, Darren pleaded. ’When hell freezes over you creep!’ was her reply.”
If you were to use this phrase “when hell freezes over”, under what circumstances would be appropriate? Try writing a sentence using the phrase.
How can you translate ‘when hell freezes over” in to Chinese?