Here is an incipient mackerel sky, looking south from the Great Lawn of Central Park in Manhattan. It should mean we have rain tomorrow: "Mackerel sky, mackerel sky. Never long wet and never long dry." In German, however, it has a different name, namely, "sheep skies." Here is from a poem of Goethe's, from 1817, inspired by the cloud classifications of the English cloud watcher Luke Howard (born in London 1772):
And higher, higher yet the vapors roll:
Triumph is the noblest impulse of the soul!
Then like a lamb whose silvery robes are shed,
The fleecy piles dissolved in dew drops spread;
Or gently waft to the realms of rest,
Find a sweet welcome in the Father's breast.