What is a cirrus cloud? It is a high, thin, wispy cloud made mostly of ice crystals.
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Short answer
A cirrus cloud is a thin, wispy cloud found high in the sky. It is made mostly of tiny ice crystals because the air at that altitude is below freezing. Cirrus clouds often look like feathers, hair, or delicate white streaks.
To answer what is a cirrus cloud in one sentence: it is a high, ice-based cloud shaped by strong upper-level winds.
Where cirrus clouds form
Cirrus clouds develop in the upper troposphere, usually higher than about 20,000 feet in the middle latitudes. At that height, water vapor freezes onto small particles and forms ice crystals. Strong winds can stretch the crystals into long strands that give cirrus clouds their characteristic shape.
What weather do cirrus clouds signal?
Thin cirrus clouds may appear during fair weather, but a growing veil of cirrus can be an early sign that a weather system is approaching. The clouds may arrive many hours before a warm front and thicker clouds bring rain or snow. Cirrus alone does not guarantee a storm; wind patterns and other cloud layers matter too.
Why do cirrus clouds look white?
Ice crystals scatter sunlight in many directions, making cirrus clouds look white during the day. Near sunrise or sunset, the crystals can reflect pink, orange, or red light. Because the cloud is thin, the blue sky often remains visible through it.
How cirrus clouds differ from other clouds
Cumulus clouds are puffy and usually lower, while stratus clouds form broad layers. Cirrus clouds are high, narrow, and fibrous. The word cirrus comes from Latin for a curl or lock of hair, which describes their appearance.
Knowing what is a cirrus cloud helps you read changing skies without assuming that every thin cloud means rain.
How high are cirrus clouds?
Cirrus clouds form in the highest part of the troposphere, often more than six kilometres above the ground. The air is extremely cold at that height, so the cloud is made mostly of tiny ice crystals rather than liquid droplets. Those crystals can bend and scatter sunlight, producing a bright halo around the Sun or Moon.
What weather do cirrus clouds signal?
A few thin cirrus clouds often appear on a fair day and may disappear without changing the weather. When they become thicker, cover more of the sky, and arrive from one direction, they can be the first sign that a large weather system is approaching. Rain or snow may still be many hours away, because the high cloud arrives before the lower, wetter parts of the system.
How can you identify a cirrus cloud?
Look for white, delicate streaks that seem brushed across the blue sky. They may look like feathers, curls, or wisps and usually have no dark, flat base. Cirrus clouds are different from contrails because natural cloud streaks spread and curve with upper-level winds, while a fresh aircraft trail begins as a narrow straight line.
Why do cirrus clouds look so thin?
The ice crystals in a cirrus cloud are widely spaced, so sunlight passes through most of the cloud. This makes cirrus look transparent compared with a thick gray rain cloud. Strong winds high in the atmosphere can stretch the crystals into long filaments, which is why the cloud often appears to move or change shape quickly.
What is the short answer?
A cirrus cloud is a high, thin, wispy cloud made mainly of ice crystals. It usually does not produce rain that reaches the ground, but a growing veil of cirrus can warn that a weather system is on its way.
For comparison, a lower stratus cloud forms a gray layer closer to the ground, while a puffy cumulus cloud grows upward. Learning the height, shape, and texture of each cloud makes identification easier.
Read about stratus clouds and compare them with cumulus clouds.
If you are wondering what is a cirrus cloud, the simplest description is a high, thin cloud made of ice crystals. Remembering that phrase helps distinguish it from the lower water-droplet clouds you see closer to the ground.
In one sentence, what is a cirrus cloud? It is a high-altitude ice cloud. The answer to what is a cirrus cloud also explains why it looks wispy instead of puffy. If someone asks what is a cirrus cloud, point to its height, thin shape, and ice crystals.