Cirrus appears as thin white strands, wisps or narrow bands with a fibrous look. It is made almost entirely of ice crystals, according to the WMO. The hooked strands in the photograph show why texture can be more informative than a simple white-versus-grey test.
We place cirrus near the top as a strong starting point for learning a different cloud shape. Trace one strand and compare its fine edges with the rounded outline of cumulus. Keep its appearance separate from predictions: seeing cirrus alone does not tell you exactly when or where rain will arrive.
Photo: ADARSHluck · CC BY-SA 4.0. Resized and recompressed; image retains its source license.
