Cirrus clouds are thin and wispy, made of ice crystals far above the surface.

The longer version

High, thin cirrus clouds sit near the top of the lower atmosphere, where temperatures stay well below freezing. There is little water vapor at that height, so the cloud is made of separate ice crystals rather than dense liquid droplets. The crystals fall slowly and are blown into streaks by fast upper-level winds.

The wispy look comes from that sparse, uneven arrangement. Because ice lets much of the sunlight through, cirrus often appears bright and translucent, and it can produce halos when the crystals happen to be shaped like tiny hexagonal prisms. They are usually too thin to cast much shade at the ground.

Where this entry sits

Clouds, wind, rain, and storms shape daily life in ways that most people barely notice. This collection explains snow, lightning, rainbows, the turning seasons, temperature, the instruments forecasters rely on, and scraps of old weather lore. The full list sits on the Weather and Climate page, where every entry is listed in order.