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What is humidity?

Have you ever felt hot and sticky in warm weather? That's because of humidity.

In this article you can learn:

  • What humidity is
  • The processes of condensation and evaporation
  • Humidity around the world
  • How to measure humidity

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

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Video - What is humidity?

Watch this video to learn about humidity and the processes of condensation and evaporation.

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Facts about humidity

  1. Humidity is a measure of how much water there is in the air.

  2. When water is in the air it's in the form of an invisible gas called water vapour.

  3. If there's lots of water vapour in the air, this means the humidity will be high.

  4. When we get hot, our bodies sweat to help cool us down. When it is humid there's already lots of water vapour in the air. That makes it more difficult for your sweat to evaporate into the air. So high humidity can leave you hot and sticky.

Discover more about sweat and how humans stay cool in hot weather here: How do humans maintain temperature and water balance?

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Humidity across the planet

Learn about humidity in the Sahara, the Antarctic and rainforests in this slideshow.

Image gallerySkip image gallerySlide 1 of 4, People relax in the park in Edinburgh, A hot and sticky summer's day If you're in the park in summer and you feel hot and sticky, this is because the humidity levels are high.
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How to measure humidity

Video - Measuring humidity

High humidity can make us feel hot and sticky.

With help from 成人快手 Weather's Kawser Quamer, learn:

  • How to measure humidity
  • How we can measure humidity using a sling psychrometer
  • How to test humidity using a sponge and a jug of water

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Key words

Key words about humidity

  • water vapour - Water in the form of an invisible gas.
  • condensation - When water vapour turns into a liquid.
  • evaporation - When water turns into a gas.
  • humidity - A measure of how much water vapour there is in the air.
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Test your knowledge

Quiz

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Challenge

Challenge

Create your own humidity experiment.

You will need:

  • A sponge
  • A jug of water
  • A tray or something to catch excess water

What to do:

  • The sponge is like the air around us. A dry sponge with no water in it can be described as 0% humidity.
  • If you add water to the sponge and it becomes so full it cannot take in any more water then it is at 100% humidity.

Watch the film above to learn more.

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