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How Are Wind, Fog and Rain Formed?


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Basics on the topic How Are Wind, Fog and Rain Formed?

Where does Fog Come From? – Simply Explained

When it's foggy outside, it can be quite eerie. But why does fog form in the first place? How fog, wind, and rain are formed will be explained below.

What is Fog? — Definition

Fog is like a cloud, but it is not in the sky, it is closer to the ground. It consists of small water droplets or ice crystals. Since fog is so close to the ground, visibility is usually very poor, which makes it hard to see when you’re driving in a car.

This is how fog is created:


There are certain conditions that need to be met for fog to form. Do you know what the most important condition for fog formation is? Fog only forms at specific temperatures. When it is warm during the day, water (for example, from rivers and lakes) evaporates due to the heat of the sun. As it evaporates, the water reduces and changes from a liquid to a gaseous state. Then, if it gets cold at night, the water vapor condenses. This means that the gaseous water vapor turns into water droplets.

When it is still warm during the day, but then becomes very cold at night, fog forms in the morning. That is why most fog occurs during autumn.

What is Wind? – Definition

Wind can be strong or weak. You can hear it, feel it, and even see it because wind is simply moving air.

This is how wind is formed:

The sun plays an important role in the formation of wind because it heats up the air. The heated air expands and rises. Up in the cooler layers of air, it cools down and descends again. The heated air creates different pressures that need to be balanced. This is how wind is formed.

What is Rain? — Definition

Rain is water droplets falling from the sky. That's why you get wet when it rains. Rain can also vary in intensity.

This is how rain is formed:

When the sun warms up the water, it rises as water vapor and cools down again up in the atmosphere. As a result, the water condenses and water droplets form. In a fair-weather cloud, these droplets are light and can move freely. As the small droplets come together, they form larger droplets that become heavier and heavier. Eventually, they become too heavy and fall as raindrops to the ground.

Wind, Fog, and Rain – Summary

Now you have learned what fog, rain, and wind are and how they are formed. In the table, you will find a summary.

Fog Wind Rain
What is it? Small water droplets or ice crystals in the air Moving air Water droplets falling from the sky
How is it formed? Fog is formed through the condensation of water. This happens when it is warm during the day and very cold at night. Wind is formed through differently heated air that creates different pressures, which then need to be balanced. Rain is formed through the condensation of water and the formation of ever-growing water droplets that eventually fall.

Frequently Asked Questions about Fog, Wind, and Rain

How do I explain fog to my child?
What is fog made of?
Is fog beneficial?
Why is there fog in winter?
Why doesn't fog fall?
Is fog moist air?
How long does fog last?
Why is fog dangerous?
How can fog be predicted?
Why does dew form at night?
What types of fog are there?
What types of fog are there and where are they common?
How is radiation fog formed?

Transcript How Are Wind, Fog and Rain Formed?

This city is dark and lost. It captivates you and never let's you go. Even the weather is a mirror of this city. The icy wind, ... The dense fog ... And the heavy rain. But the big mystery is ... How Are Wind, Fog, and Rain Formed? The icy wind makes an almost musical whistling sound. But where does the wind come from? The power of the sun plays an important role in creating wind. It heats the air. The heated air particles expand, becoming lighter, causing them to rise. Layers in the atmosphere, cool them again ... and they sink back down. The movement of the heated air particles rising, along with the cool air particles sinking, creates wind. The zone where air particles rise is known as a low-pressure area. In a low pressure area, the weather is often cloudy or rainy. Sometimes it even snows. On a weather map, low pressure is often shown using THIS symbol. The zone where the air particles sink down is called a high-pressure area. The weather is nice in this area. The sky is blue and clear. Can you guess which symbol we use for high-pressure? On a weather map, high-pressure is often shown using THIS symbol. Let's see what Wilma is doing! If the wind dies down, fog can move in silently over the streets. But how is fog formed? Have you ever walked through fog? If you have, then you know you can't see far. Fog is like a cloud on the ground. Like a cloud, the fog consists of many small drops of water, or ice crystals. Fog forms more often near bodies of water. If it is hot during the day, the water evaporates through the warmth of the sun. Water changes from a liquid to a gaseous state during evaporation, known as water vapor. For example, you may have seen a puddle of rain that disappears, or evaporates, after the sun comes out. If it is cold at night, the water vapor condenses. As the warm air cools down again, the gaseous water vapor becomes water droplets. Do you which season is often warm during the day and is very cold at night? Autumn, therefore we may see a lot of fog during this season. A rain coat protects you from the rain, so you don't get wet. (...) But how is rain formed? Condensation plays a role in creating rain. The heated water rises as water vapor. And then cools down again. To form water droplets. These water droplets move back and forth in the cloud. When the small drops come together, large drops are created, which makes it difficult for them to move. When they become too heavy, they fall down to the earth as raindrops. Today we learned how wind (...), fog (...) and rain (...) are formed. We also learned that the sun plays an important role. So the big weather mystery is solved. But there is still one big question left: why is everything black and white here?


How Are Wind, Fog and Rain Formed? exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video How Are Wind, Fog and Rain Formed?.
  • What is the weather often like in a low-pressure area?


    There are 2 correct answers.

    In a low-pressure area, the weather is never described as sunny.


    The weather in a low-pressure area is often cloudy or rainy.

  • How is wind formed?


    When air particles are heated, they expand.

    The cool air particles sink because they are heavy.


    When air gets heated it expands, making its particles spread out.

    As the air expands, it becomes lighter because it takes up more space.

    This lighter, heated air rises upward in the atmosphere.

    The cool air particles sink, this creates wind.

  • What is a cloud on the ground?


    Like a cloud, the fog consists of many small drops of water, or ice crystals.

    Fog forms when warm air cools down, causing water vapor in the air to turn into tiny water droplets, creating a cloud near the ground.

    This often happens near water bodies and during cooler nights.


    Fog is described as a "cloud on the ground".

    It forms more often near bodies of water, and is more common during seasons like autumn when there are warm days and cold nights.

  • Can you match each of the following weather descriptions with the appropriate weather type?


    Think about what kind of weather is usually associated with each description.

    For example, what type of weather is typically associated with a clear, sunny sky?

    Look at the list of weather types and try to match them with the descriptions based on your understanding of different weather conditions.


    The matches for the weather descriptions and weather types are:

    • Clear sky, bright and sunny: sunny
    • Dark clouds, heavy rain: rainy
    • Thick mist, can't see far: foggy
    • Strong wind, things moving around: windy
    • White flakes falling, ground covered: snowy
    • Gray clouds, possible rain: cloudy
  • How is the weather in high-pressure and low-pressure areas defined?


    High-pressure areas are associated with clear skies and good weather.

    Think about the effects of the sun's heat on air particles, water evaporation, and the water cycle.

    • High-pressure areas usually mean good weather with clear skies and sunshine.
    • Low-pressure areas usually mean less pleasant weather with clouds, and the possibility of rain or storms.
  • How are raindrops formed?


    Condensation plays a role in creating rain by making heated water rise as water vapor.

    The water droplets combine to form larger drops which become too heavy.


    The correct order is:

    • Raindrops are formed when water from the ground rises up into the sky because of the sun's heat.
    • In the sky, this water turns into tiny drops which join together to make bigger drops.
    • When these drops get heavy, they fall down as rain.