What are congruent expressions for "rain cats and dogs" in other languages?
In Serbian language, we often use an expression „sekire padaju sa neba“ which literary means „axes fall from the sky“, but figuratively connotes bad weather. The expression has its roots in Slavic mythology.
Perun was the god of thunder and lightning. According to the myth, he had the famous ax, which, when dropped to the ground, it would cause not just a thunderstorm, but it would turn everything to the stone.
In Serbian language is often heard the sentence „Idem napolje makar i sekire padale sa neba.“ ("I'll go out even if the axes fall from the sky.") That means that any bad weather conditions will not change our plans.