There are two things going on to make some rain clouds to appear very dark. The first is that some clouds, especially thunderstorm clouds such as nimbocumulus clouds can tower to great heights with tops 15 to 20 km (50-60 thousand feet) above the earth. Plus these clouds, which tend to produce very heavy rains and hail are very dense, being full of water vapor and raindrops at lower altitudes and ice crystals at high altitude.
As a result, it is more difficult for sunlight to pass through these clouds than it is for light to pass through neighboring clouds which aren't as high and dense. More of the light is reflected back into space or sideways because there's more obstacles. Plus, there's more absorption of the light on its way through the cloud, because the light will bounce around very much and take a very long total path before finally coming out the bottom of the cloud.
Nimbostratus clouds.
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The clouds that can become extremely large, black, and ominous on hot summer days are called cumulonimbus clouds. These towering clouds are associated with thunderstorms and severe weather, often characterized by their anvil-shaped tops and dark bases. As they develop, they can produce heavy rainfall, lightning, hail, and even tornadoes, making them a significant weather phenomenon during the summer months. Their dramatic appearance is a result of intense updrafts and moisture in the atmosphere.
Cumulonimbus clouds can become extremely big, black, and ominous-looking on hot summer days. These clouds are associated with thunderstorms, heavy rain, lightning, and sometimes hail. They can develop rapidly and contain strong updrafts and downdrafts that create turbulent weather conditions.
When there are dark clouds in the sky, it is a sign that a rain shower is eminent. Clouds full of precipitation are much more dense than other clouds and as a result less sunlight can shine through causing the clouds to appear black.
White. But gray sometime when raining
Clouds can turn black when they are full of moisture and become thick and dense. This can happen before a heavy rainstorm or thunderstorm, as the clouds block more of the sunlight and give the appearance of being black. Additionally, pollution or smoke in the atmosphere can also make clouds appear darker.
Nimbostratus clouds.
Actually, clouds are sometimes black. Storm clouds are.
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A dark rain cloud is called a nimbus. These clouds produce rain and snow as they are filled with compact and frozen moisture.
Nimbus … rain clouds
black clouds and feathered clouds
Clouds appear black when they are thick and dense, blocking out sunlight and making them appear dark. This can happen when there is a lot of moisture in the air, causing the clouds to absorb more light and appear black.
Dark rain Clouds are clouds that are black when it rains
Dark rain Clouds are clouds that are black when it rains
The only difference between dark clouds and light clouds are they're thickness. A dark cloud is thikcer than a light cloud so it doesn't let as much light through. SO to answer your question, clouds are black in the rainy season because they are "holding" more water than they hold during the dry season