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What is fog?

We see fog mainly in autumn and winter. Fog is cold and damp and makes it difficult to see. Where does it come from?

In this article you can learn:

  • How fog is formed
  • Different types of fog and how we measure it
  • The difference between fog and mist
  • How different places around the world use fog

This resource is suitable for weather topics for primary school learners.

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Video - What is fog?

Watch this video to learn about fog and mist.

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How does fog form?

  1. Fog usually appears after rain, when there is a lot of in the air.

  2. When the ground cools down, so does the air near it.

  3. When the air cools down it can't hold so much water vapour.

  4. So the water vapour condenses into cloud droplets - which we see as fog.

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Foggy days and fogbows

Click through this slideshow to discover more about fog around the world.

Image gallerySkip image gallerySlide 1 of 6, A girl breathing on a cold day. Her breath is visible., Foggy breath When you breath out on a cold day and see your breath, you're making your own cloud of fog!
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What is the difference between fog and mist?

Weather forecasters describe fog in different ways depending on how thick it is.

  • dense fog - if you can鈥檛 see more than 50 metres ahead of you.
  • thick fog - when you can鈥檛 see further than 180 metres.
  • mist - if the fog is thin enough so that you can see one kilometre away.

Fog of all kinds can affect our lives and the world around us. Learn more here: How does fog affect our daily lives?

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Key words

Key words about fog

  • fog鈥 A cloud that has formed near the ground.
  • dense fog 鈥 When you can鈥檛 see further than 50 metres.
  • thick fog 鈥 When you can鈥檛 see further than 180 metres.
  • mist鈥 When the fog is thin enough that you can see one kilometre away.
  • fog bow 鈥 A fog bow looks like a rainbow, but is pale and hazy instead of colourful.
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Test your knowledge

Quiz

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Challenge

Challenge

Create and give a presentation about fog.

This article is full of information about fog and how it can be used in different ways across the world. Can you explain what you have learned in a presentation?

Before you give your presentation, you might want to think about some of these tips:

  • Remember to prepare any points, slides and props you might have.
  • Think about who your audience is.
  • You can use graphs, charts or quotes to support your ideas.
  • Make eye contact with the audience and speak clearly.

If you need more help on giving a presentation, here is a video to help: How to give a presentation.

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