Ever wonder about the phrase “It’s raining cats and dogs”? Most people recognize this as a description of a fierce rain shower, but have you ever seen cats and dogs pouring down from the sky?
The folklore behind the saying has two parts. A lightning strike in European folklore (and in some other places, such as the Philippines) is associated with a dog bite. That makes sense: electricity has a bite to it, so being struck by lightning probably would feel like a dog bite.
What about the cats? There is also a longstanding belief in folklore that cats cause it to rain by vigorously washing their faces.
So, raining cats and dogs refers to a type of storm where there is torrential rain (caused by the cats) and lightning (biting dogs).