What is humid?

Humid means the air feels heavy and sticky because it has lots of water vapor in it.

Imagine you're playing outside on a hot day, and you take a big sip from your favorite juice box. The more juice you drink, the heavier your belly feels. That’s like what happens with humid air, it's like the air is full of invisible juice, making everything feel heavier and stickier.

When the sun shines on water, like a lake or a puddle, it turns some of that water into vapor, which is just tiny drops of water we can’t see. This vapor goes up into the air around us. If there's already lots of vapor in the air, and the temperature stays high, the air becomes humid, like when you're wearing a wet shirt on a hot day, and your skin feels all sticky.

You can tell when the air is humid because your skin feels sticky, or your hair looks like it's been in a soup. It's also easier to feel tired when it's humid because our bodies have more work to do, they need to sweat to cool down, but the vapor in the air makes it harder for that sweat to evaporate.