When pigs fly

When something is impossible or very unlikely to happen, you might say it will happen only when pigs fly, when hell freezes over, or on a cold day in hell. Or that it won’t happen in a month of Sundays.

Flying pigs are also uncommon in Norweigan (Når griser flyr), Romanian (când o zbura porcul), Swedish (När grisar flyger) and Welsh (Pan fydd moch yn hedfan).

In Catalan it’s cows that are unlikely to fly – quan les vaques volin. The same is true in Finnish (Kun lehmät lentävät), and Italian (Quando voleranno gli asini).

The temperature of hell is unlikely to fall below zero in Danish (Når helvede fryser til is), Finnish (Kun helvetti jäätyy), German (Wenn die Hölle zufriert), Hungarian (Majd ha a pokol befagy), Swedish (När helvetet fryser till is), and Welsh (Pan fydd uffern yn rhew drosodd).

Equivalent idioms in other languages include:

  • Bosnian – Kad na vrbi rodi grožđe – When grapes ripen on the willow
  • Danish – Når der er to torsdage i en uge – When there’s two Thursdays in a week
  • French – Quand les poules auront des dents – When chicken have teeth
  • German – Wenn es im Sommer schneit – When it snows in summer
  • Hindi – Sooraj pashchim se ugega – When the sun rises in the west
  • Latvian – Kad pūcei aste ziedēs – When the owl’s tail blossoms
  • Malayalam – Kakka malannu parakkum – The crow flys upside down
  • Spanish – Cuando las ranas críen pelo – When frogs grow hair
  • Ukrainian – Koly rak na gori svisne – When the crayfish on the hill whistles