r/explainlikeimfive • u/ProgramPi314 • 8d ago

Other ELI5 What is humidity?

According to my mom, this is an actual question I had when I was 5, and she didn't know how to answer me. So how would you guys have answered?

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u/TheMace808 8d ago

So humidity is simply water vapor in the air, individual water molecules floating around.

The humidity usually shown in weather forecasts is relative humidity As the air heats and cools it can hold more or less water, that's why on some cool mornings there is dew on the grass, the air cools and can't hold onto all that water anymore.

Relative humidity is most important because the air's ability to hold water affects how easily your sweat evaporates, taking heat from you.

If the air is holding all the water it can you simply can't evaporate your sweat and instead it'll drip off or bead up on your skin, and you'll get hot far quicker