I always thought that the expression "raining cats & dogs" is becuase before animals were not house pets, but lived outside, and during a heavy rain cats and smaller dogs would get washed away down the street, hence making it look like they had falled with the rain.
I always thought that the expression "raining cats & dogs" is becuase before animals were not house pets, but lived outside, and during a heavy rain cats and smaller dogs would get washed away down the street, hence making it look like they had falled with the rain.