A vocabulary of landscape — a landscape of words
1469 entries
mackerel sky
A mackerel sky is a sky filled with rows of small rounded cloudlets in a regular rippled pattern, high enough to be cirrocumulus or altocumulus. The name is for the resemblance to the barred blue-and-silver flank of a mackerel. It forms where a moist stable layer is being gently overturned, and it commonly runs ahead of an approaching front.
Etymology
The term is a sailor’s and it is old, appearing in English weather lore for centuries. The American version of the same observation is buttermilk sky, on this site, which sees curds in churned milk instead of fish. Both names sit alongside the Latin, which tells you the altitude, while the folk name tells you what it looks like from the ground.
Notes
The rhyme about a mackerel sky meaning never long wet and never long dry gets at something real, since the pattern rides on a front and fronts move through. The fuller version pairs it with mares’ tails and the two together are a good indication of a warm front approaching within a day.