it'll be a cold day in hell

it'll be a cold day in hell

It is unlikely or impossible that it will ever occur. Used hyperbolically and often issued in defiance of some request or demand. It'll be a cold day in hell when I sign over the lease of my land to you. It will be a cold day in hell before the two parties agree to anything.
See also: cold, hell
Farlex Dictionary of Idioms.

It'll be a cold day in hell (when something happens).

Rur. Something will never happen or is highly unlikely. It'll be a cold day in Hell when the city council agrees on where to build that bridge. It'll be a cold day in Hell when I forgive you.
See also: cold, hell
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • catch (one's) death (of cold)
  • catch death
  • catch one's death (of cold)
  • catch your death
  • chance of a lifetime
  • can't get over (something)
  • can't get over something
  • everyone and their brother
  • (someone's or something's) days are numbered
  • days are numbered, one's
References in periodicals archive
We're always being told to use public transport more but I'm sorry, it'll be a cold day in Hell before I shell out that amount for a bus journey into Stirling.