This article was originally published in 2018 but has been updated to include relevant content and additional information.
From watching the clouds drift through the sky on a lazy Sunday afternoon to getting your picnic rained out from seemingly clear blue skies, we've all thought about those beautiful white things in the sky in one way or another. When considering cloud development and cloud types, there are three main cloud categories to understand: vertical developing clouds, layered clouds, and light, icy clouds. Read on to learn which types can be considered harmless, fair-weather clouds and which types require your close attention, as they may lead to thunderstorm and lightning development.
Vertically Developing Clouds
Vertically developing clouds are created as moisture from the ground rises, cools, and condenses, creating fluffy, white, billowing clouds. There are two common types of vertically developing clouds:
If the atmosphere is stable, which means the air is not rising, then these cumulus clouds will not continue growing vertically and further cloud development is not likely. Cumulus is Latin for "heap" or "pile," and these clouds form and look like just that: a heaping pile of billowing white fluffiness! These are what we call fair-weather clouds that make for some neat shapes as they drift by.
If the atmosphere is unstable, which means the air is rising, warm air from the Earth’s surface continues to rise. As it rises, it continues to cool and condense, leading to further cloud development that allows these clouds to continue to grow vertically taller and taller. These clouds can lead to thunderstorm development with heavy rain, lightning, and even tornadoes!
Low-level, layered clouds that are uniform and often covering the entire sky are called stratus clouds.
Stratus clouds can create drizzle or mist, but usually do not bring rain. Fog is low stratus clouds that are touching the ground. Strato is a Latin prefix meaning “layer.”
Light, Icy Clouds
Light and icy clouds are called cirrus clouds and develop in the atmosphere's highest levels, where it's extremely windy and so cold that only ice can form. There are four main types of high-level, light and icy clouds:
These high-level clouds, made of light, fibrous ice crystals, get easily blown around to appear wispy and thin in the sky. Precipitation from these clouds does not reach the ground, but ice can fall from them, which create fall streaks or virga (precipitation that doesn't reach the ground). Cirrus is Latin for "curl of hair," which is why these clouds are often called "mare's tails."
Altostratus are high-level, layered clouds that can look like a thin blanket of clouds in the mid-to-upper levels of the atmosphere.
These are high-level, puffy clouds. Altocumulus can be patchy or grouped together but clearly show distinguished clouds.
Cirrostratus clouds are a high-level, icy cloud with a thin bottom layer that looks like it covers the entire sky with a thin sheet of ice. This can be clearly seen when you get the halo effect around the sun or moon during otherwise clear skies.
Cloud names are derived from these three categories based on their characteristics and height in the atmosphere.
We pair more Latin words together to get more specific on describing clouds. For example, alto (Latin for “high”) can describe various types of clouds like an altocumulus or an altostratus. Nimbus (Latin for “rain”) is a description that’s used if rain accompanies the cloud – such as nimbostratus or cumulonimbus. Check out the image above to learn more about what Latin words combine to describe different cloud types. Cirrostratus? A high-level, icy, layered cloud!
A descriptor, nimbus (Latin for “rain”), accompanies a cloud name once precipitation is associated with the cloud.
Nimbus is rarely a term that describes a specific cloud on its own. It's used to add the "rain" description to the name of a layered or vertically developing cloud. Nimbus clouds are already producing rain or snow and, as a result of their moisture content, look dark in color. Some examples of nimbus clouds are:
This is a low, layered cloud and usually looks like a grey blanket covering the sky with rain falling from it. In cold temperatures, snow falls instead of rain.
As mentioned above, this is a type of vertically developing cloud that grows taller and stronger, with enough moisture to produce precipitation that can lead to periods of heavy rainfall and thunderstorm development.