Oh, I had no idea that was a real thing. (Sometimes the sources are obscure and very non-literal. In this case, I guess not...) Apparently it was in the 17th century, with rain so hard that it would wash away pets, rather than actually having them fall from the sky. Interesting.
As for "beestenweer", that may be my new favorite word in Dutch, not that I know all that many up to this point.
I don't think any of that has been documented. I've heard of it raining frogs as well. Though it has been theorized tornadoes/water spouts might be an explanation, nothing has been caught on film or otherwise documented that could prove the veracity of these claims. I like Daniel's idea of the "rain so hard that it would wash away pets, rather than actually having them fall from the sky". But who knows for sure?
I'm thinking that beestenweer might just be, "It's not a fit night out for man nor beast." with a bit of fanciful back story thrown in for 'fun', or a sort of urban legend (probably given the date when this was supposed to have occurred, more like a rural legend.)
Note: what I said was from one of the first Google links that comes up searching for Yorkshire+'raining cats and dogs'. I don't know that it's true, but it seems plausible to me.
I must confess that I made up all I said in post #10, except for the expression beestenweer. That's a genuine expression of Dutch.
Sometimes it's fun to just let your imagination go.
As far as I understand from English folklore, "raining cats and dogs" came about from when small animals climbed up into the thatch roofs of English oldy-worldy houses to get away from stormy weather. Anyway, if the weather was *really* bad, and especially on houses of poor people who couldnt afford proper thatch or repairs, the rain would totally saturate the thatch/straw to the point where the small animal hiding inside would fall through onto the occupants below. Coincidentally, this is supposed to be the reason for canopies above beds - to catch the animals before a soggy cat landed on your head and woke you up ;)
Haha, I really like that explanation Beverley.
Most of what is being discussed here is known as "folk etymologies". But some might be right.
According to this generally reliable source, no one knows: