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All About Weather

Look up: Puffy clouds are here

cumulous clouds

If you ever take a few minutes to watch what happens to clouds in the sky, especially in March, you’ll see many puffy shaped clouds form and fall apart. You’ll see these clouds at other times of the year, but they are around a lot in March and April.

What clouds are puffy?

Cumulus clouds form within a few hundred to few thousand feet above ground. They form from surface heating of the earth. Imagine a bunch of air bubbles being warmed by the land below them and acting like hot air balloons. 

Unlike balloons, as these bubbles of air rise, no heat is added to them. The bubbles expand because they are moving into higher and thinner air with less air pressure. This expansion causes them to cool. As air cools, its ability to hold water vapor, the gas form of water, decreases. 

If the air cools to the point it can’t hold the water vapor it started out with, some of the water vapor will have to condense into liquid water. A cloud starts to form! The cloud will grow as the air rises and stops growing when the air stops rising.

Cool things to watch for

As the sun continues to get higher in the sky in March and April, the earth’s surface is heated more intensely, creating more air bubbles and cumulus clouds. Typically, we may start the day with a clear blue sky, then start seeing small cumulus clouds by mid-morning as the surface heats, and a bunch of clouds by midafternoon. They quickly disappear by evening as the sun sets and the earth's surface is no longer being heated, leaving a clear sky again.

By watching the sky for periods of time, you may see cumulus clouds form and then quickly fall apart as strong winds at that altitude tear the cumulus clouds into pieces, especially if there is not much vertical growth. The remnants of these cumulus clouds are given the name fractus.

Cumulus clouds that are not growing very tall are also known as "fair weather" clouds. They indicate air is not rising very high and not creating thunderstorms.  

What happens later in the spring and summer

By the time we get into May through summer, there is more heating, and you’ll see cumulus growing taller. In some cases, they may grow tall enough to produce a thunderstorm, but not every time. Upper air winds get weaker as well, making it harder to tear cumulus clouds apart.


ABOUT THE BLOG: All About Weather explores the environment, climate, and weather topics for Illinois. Get in-depth information about things your weather app doesn't cover from summer droughts to shifting weather patterns. Never miss a new post! Sign up for our email list.

MEET THE AUTHOR: Duane Friend is a state master naturalist and climate change specialist with University of Illinois Extension, serving the organization in many roles since 1993. Duane provides information and educational programs to adult and youth audiences in the areas of soil quality, weather and climate, energy conservation, and disaster preparedness. These programs provide practical solutions for families, farms, and communities. He assists families in creating a household emergency plan, farmers with the implementation of soil management and conservation practices, and local government officials and business owners with energy conservation techniques.