Knowing which types of clouds produce precipitation can help you plan the best activities. The types of clouds you see can provide you with the knowledge needed to stay dry and safe. Almost all rain is produced from low-level clouds. Stratus clouds produce steady rains, and cumulus clouds produce intense, stormy precipitation. Mid-level clouds can tip you off to the potential for these precipitation-producing cloud types to develop and may even produce an occasional sprinkle themselves.
Cloud Type Basics
Clouds are classified into 10 types, plus fog and contrails. These clouds are then defined and named based on their altitude, shape and precipitation. Cloud levels are expressed with a prefix. Low-level clouds, from the surface to 6,500 feet, have no prefix. Mid-level clouds, from 6,500 to 20,000 feet, have the prefix alto. High-level clouds, above 20,000 feet, have the prefix cirro. The four main types of clouds are cumulus, cirrus, stratus and nimbus. Finally, clouds producing significant precipitation include the prefix or suffix nimbo. By combining these terms, you produce a unique name for all 10 of the primary cloud types.
Nimbostratus clouds are low-level, rain clouds that form a uniform layer. These layers cover the sky, producing overcast conditions, and uniformly extend in all directions. They are dark in color and produce steady, prolonged precipitation. They represent a strengthening and thickening of a stratus cloud layer. While stratus clouds are renamed nimbostratus when precipitation becomes significant, stratus clouds themselves can produce occasional, light precipitation.
Cumulonimbus clouds are large, puffy clouds with strong vertical development. They are formed by the upward movement of warm, moist air. In their mature stage, they also produce strong downdrafts of cold air. Cumulonimbus clouds are considered low-level clouds, even though their vertical development may extend high into the atmosphere. These clouds produce intermittent, intense precipitation and are associated with severe weather. Strong cumulonimbus storm cells can produce thunder, lightning, hail, torrential rains, strong winds and tornadoes. Cumulus congestus clouds, having more vertical development than fair-weather cumulus clouds, can also produce light rain, though not significant enough to warrant a name change to nimbus.
Other Precipitation-Producing Clouds
Though the two nimbus cloud types are responsible for the vast majority of precipitation, there are two mid-level cloud types that can also produce occasional precipitation. Altocumulus clouds are simply cumulus clouds at a higher altitude. These puffy, white clouds often indicate an approaching front and the potential for the development of precipitation. Though they don’t generally produce precipitation themselves, they can occasionally produce sprinkles or light showers. Altostratus clouds are simply higher-level stratus clouds. These cloud layers may also indicate the approach of a front. When the cloud layer thickens and descends, it becomes a stratus or nimbostratus layer, depending on precipitation. Like altocumulus clouds, altostratus clouds do not produce significant precipitation; however, they can produce sprinkles or occasional light showers.