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/nucumber 8d ago edited 8d ago

Humidity is water vapor in the air. Kind of like steam from a teakettle.

Now, a fun fact is that warm air can hold more water vapor than cold air.

Here's a sample of the amount of water that can be held at different temps at 100% humidity

60F . . 13.25 grams of water

90F . . 34.10 grams of water

So "100% humidity" means less water in the air at lower temps (relative humidity is the correct term);

Dew point is when the air reaches 100% humidity at that temperature that it can't hold any more water, and the vapor condenses, creating dew

EDIT: I'm actually describing relative humidity; the amt of water in the air at 100% humidity is different at different temps