Most languages have a popular term or a traditional saying for the occurrence of rain while the sun is shining (a sunshower). Most of these expressions have been handed down from generation to generation and it may be difficult to trace their origin.
My question is about the most common term in your English speaking country, (mention where you're from) its origin and, in case it's not obvious, an explanation why people call it that.
EDIT - This other question, mentioned as a possible duplicate in one of the comments, is about "rain without clouds" which is clearly different from "the simultaneous occurrence of rain and sunshine".
I'm not looking for lists. I'm looking for the most popular and traditional saying in the US, the UK, in Australia, etc. A saying most people will have heard at some time during their lifetime.