Frequently Asked Questions

The international cloud-classification system recognizes ten main cloud genera, commonly called the ten cloud types: cirrus, cirrocumulus, cirrostratus, altocumulus, altostratus, nimbostratus, cumulonimbus, cumulus, stratus, and stratocumulus. They are commonly organized by the altitude where their bases usually form, although their levels can overlap and vertically developed clouds can extend through more than one level.

Start with the cloud's approximate height, overall shape, and whether it forms a layer, patch, heap, tower, veil, or fibrous streak. Then check its sky coverage, shading, vertical growth, and precipitation. Cloud identification works best by combining several visible clues rather than relying on one feature. The cloud identification guide walks through this process step by step.

Begin with the ten cloud types to learn their names, altitude levels, and broad visual differences. Next, use the cloud identification guide to learn a repeatable observation process. The cloud classification lessons are the best place to practice with real photographs.

A photograph can provide useful clues, especially when it shows the surrounding sky, horizon, cloud edges, texture, and precipitation. A tightly cropped image may hide important context such as scale, coverage, and nearby cloud layers. When possible, compare a wide view with a closer photograph and note how the cloud changes over time.

A cloud type, or genus, is the starting point for every classification. Subtype terms add detail when they apply: a species describes form, a variety describes arrangement or transparency, and additional terms can identify supplementary features, accessory clouds, or other clouds and their origins. A cloud does not need every subtype category to have an accurate classification.

Nimbostratus is commonly associated with widespread, persistent rain or snow, while cumulonimbus can produce showers, thunderstorms, lightning, hail, and strong gusts. Other cloud types can also produce drizzle, light precipitation, or precipitation that evaporates before reaching the ground. Consider precipitation together with the cloud's structure, coverage, and vertical development.

The printable cloud identification chart places the ten cloud types and their compatible species, varieties, supplementary features, accessory clouds, and other clouds together in one visual reference.