"The Rain In Spain"

There is an overworn poem that explains the rain in Spain: at least when it rains. It cites, "...the rain falls mainly upon the plain." But wouldn't that condition be a pain? If rain falls mainly where it's flat, what happens to the dogs and cats? 'Cause some say it rains them too. So say now you, what is one to do? And, exactly where would the water flow? As for me, I do not know. And if the droplets are serene, falling gently with no strain, that could be a pleasant scene. The fertile plain reborn again. Out on those lovely plains in Spain, in the rain.