A vocabulary of landscape — a landscape of words
1068 entries
buttermilk sky
A sky filled with small rounded cloudlets in a regular curdled pattern, evenly spaced and often in rows — altocumulus or cirrocumulus, high enough to be lit warm at either end of the day. The formation means moist air in a stable layer being gently overturned, and it commonly runs ahead of an approaching front, which is where the weather lore attaches.
Etymology
American English, from the look of churned buttermilk with the curds still suspended in it — the same observation as the older sailor’s term mackerel sky, which sees fish scales instead. Both names are pre-scientific and both are still in use alongside the Latin, which is the usual situation in weather vocabulary: the official word tells you the altitude and the folk word tells you what it looks like from the ground.