This story originally appeared in the Morning Brief email newsletter. Sign up here to get more stories like this and weekday weather updates from The Weather Channel and our meteorologists.
Here's a weather phenomenon that is both pretty easy to recognize and helpful in terms of knowing what kind of weather could be coming your way soon. A mackerel sky describes rows of cirrocumulus or altocumulus clouds that have an undulating, rippling pattern reminiscent of fish scales.
There's a classic rhyme passed down through weatherlore that goes "mackerel sky, not twenty-four hours dry." And indeed, mackerel skies often indicate that the weather is about to change. That's because cirrocumulus and altocumulus clouds are both fairly high-level clouds influenced by upper-level winds, often typical of advancing warm fronts or low pressure systems.
When you see a mackerel sky, you can usually expect the clouds to start thickening with moisture within about 12 hours as the weather system approaches. As they thicken, the clouds will extend downward to become low-lying clouds that bear rain.
Ready To Learn More? Here Are Some Recent Weather Words You May Have Missed:
Y?ou can find our entire archive of Weather Words here.
The Weather Company's primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.