Riding this evening, I exclaimed, "Wow, look at that mackerel sky!" My husband said he'd never heard that term. I pointed to the pink and purplish striations in the clouds and said, "It's supposed to resemble fish scales." I told him it's supposed to be an indicator of rain. I repeated the old couplets:
"mackerel in the sky,
three days dry"
"mackerel sky, mackerel sky,
never long wet, never long dry"
I asked, "Have you heard of buttermilk sky?" He said that he had. (Of course, I started singing "Ole Buttermilk Sky", from my mother's repetoire.) I said, "Buttermilk sky is the same as mackerel sky." He said, "Well, I've seen a mackerel and I've seen buttermilk and they don't look the same!"
I guess it's poetic license.