Cirrus are high, ice-crystal, filamentous clouds forming in cold, moist upper tropospheric conditions. They act as harbingers of weather change. Named scientifically in the early 19th century by Luke Howard, they have long been used in art and poetry to evoke sky texture.
Cirrocumulus are small, finely textured clouds of ice crystals in a high layer, appearing as ripples or patchwork. They form under weak vertical motion. The term was formalised in 19th-century cloud atlases, and the “mackerel sky” phrase has long circulated in folk weather lore.
Cirrostratus are high, veil-like ice-crystal clouds that spread diffusely and often produce halos around the sun or moon. They form under gentle ascent near warm fronts. Their name solidified in standard cloud atlases from the late 19th century, and they feature in halo folklore.