Environment
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What are Stratus Clouds?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Stratus clouds are low-lying, uniform clouds that blanket the sky. They are often a dullish white to gray in color, and they are generally the sort of clouds that appear when people talk about a “cloudy day.” Stratus clouds are not generally associated with poor weather, although they can be accompanied by drizzle, and at higher altitudes, they can be an indicator that rain is on the way.

These clouds are among the lowest of cloud formations, and in fact, sometimes they creep so low that they turn into ground-based fog. They are characterized by having horizontal layers with an extremely even, uniform bottom. In Latin, “stratus” refers to a layer or blanket, and these terms are very apt descriptions of classical stratus clouds. Sometimes, the clouds will appear in a more fragmented way, as is the case with stratus fractus.

Nimbostratus clouds are associated with rain and oncoming storms.
Nimbostratus clouds are associated with rain and oncoming storms.

Altostratus and cirrostratus are two forms of clouds that appear higher up in the troposphere, while nimbostratus are associated with rain and oncoming storms. These clouds can also create a halo effect around the moon and stars when they are thinner and more hazy. On a very cloudy day, the sun may be totally obscured by them, or it may appear in the form of a blurry bright patch in the cloud cover.

The troposphere is the layer of the Earth's atmosphere that comes into contact with the ground.
The troposphere is the layer of the Earth's atmosphere that comes into contact with the ground.

Sometimes, lighting conditions under stratus clouds can be very interesting. These clouds have a tendency to dull the light, creating a flattened look that filmmakers sometimes use to set a specific mood or tone. Many people find them rather boring, because of their uniform bottom, although they can get more interesting when they are fragmented beneath other clouds in the atmosphere. When stratus layers become extremely fragmented under higher clouds, it can be a warning that bad weather is on the way.

Stratus clouds are often so low that they turn into ground-based fog.
Stratus clouds are often so low that they turn into ground-based fog.

Like other clouds, the stratus variety are formed when water vapor condenses. This is typically caused by a flow of warm, moist air that flows into a block of cooler air. As a result, these clouds often appear on very muggy days, when the air is high in moisture. In urban areas, low-lying clouds can also trap pollution, making people feel very dirty and sticky by the end of the day as a combined result of humidity and pollutants.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

anon152424

This is very helpful. I am doing a project on weather that my teacher made up on the spot. School is hard. Very hard. Especially when you're at college prep one. Great info!

upnorth31

My kids love foggy days. They get so excited to know that when we are driving through fog, we may be actually driving through stratus cloud formation that is low to the ground.

I think that knowing we are driving through clouds makes them feel like they are flying. Cloudy, or foggy, days are not gloomy ones for our family. They are full of fun and imagination.

rosoph

Whenever I see a cloudy day, I expect it to rain. I didn't know that stratus clouds generally are not rain clouds. It helps to know that, when planning outdoor activities. I'm always a bit nervous about doing things outside on a cloudy day.

claire24

I find this so interesting. I have always been interested in weather, and learning about the different kinds of clouds and what they mean. I just love studying the clouds and the differences in how they look.

I really like it when stratus clouds are low in the sky, with other types of clouds moving at different speeds above them. I could just sit and watch the clouds all day!

I even have a stratus cloud picture hanging on my wall, where you can see the sun just barely glowing through them, above the horizon. It's one of my favorites.

mankygoat

What is the average thickness of a stratus cloud layer on a cloudy day?

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    • Nimbostratus clouds are associated with rain and oncoming storms.
      By: powerzilly
      Nimbostratus clouds are associated with rain and oncoming storms.
    • The troposphere is the layer of the Earth's atmosphere that comes into contact with the ground.
      By: designua
      The troposphere is the layer of the Earth's atmosphere that comes into contact with the ground.
    • Stratus clouds are often so low that they turn into ground-based fog.
      By: veneratio
      Stratus clouds are often so low that they turn into ground-based fog.