What is humidity?

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

In this article you can find out:

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

This resource is suitable for Weather topics for P2, P3, P4, P5, P6 and P7 (First and Second Level Curriculum for Excellence).

Watch this video to learn about humidity.

What is 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.

Humidity across the planet

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

High humidity can make us feel hot and sticky. With help from BBC Weather's Kawser Quamer, let's find out:

  • How humidity is measured using a sling psychrometer
  • How to test humidity using a sponge

  • 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.

Test your knowledge of humidity with this short multiple choice quiz.

Create your own humidity experiment.

You will need:

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

The sponge is like the air around us.

  • When the sponge is dry with no water in it, 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 find out more.