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Mackerel Sky Sunset
A "mackerel sky" adds to a striking sunset scene in Grimsby, Lincolnshire, England. Ripples of altocumulus or cirrocumulus clouds—resembling the markings of a king mackerel—give the phenomenon its name.
Photograph by John Leslie/Alamy

Clouds

See pictures of different cloud types (cumulus, lenticular, and others) from National Geographic.