Eli5: What humidity means and it’s percent


Eli5: What humidity means and it’s percent

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very simply: its the amount of water vapour in the air, expressed as a percentage of what the air can “carry” as water vapor.


Once it gets to 100%, the air cannot carry any more water as a vapor, and it condenses into fog or clouds.

When you have air, it contains a lot of things. For example oxygen that we breath, but also other elements like nitrogen. And it also contains water. Not the water you drink, but vapour, gas state of water. But air can contain only so much water. And thats what humidity tells you. The percent of humidity is what percent of maximal amount of vapour does the air have. When you have 70% humidity, it means that there is 70% of vapour the air can contain at given situation, because temperature and pressure can influence it. Humidity of 100% means that air cant contain any more of vapour.

the air is like a bucket, and as humidity goes up the bucket can only contain so much water. temperature determines how big the bucket is, when the air is hot the bucket is bigger and can hold more water, and vice versa. the dew point is the temperature that would cause the humidity to reach 100% and start condensing onto surfaces, given the amount of water currently in the air (shrinking the bucket). a raincloud starts pouring when its humidity reaches 100% and it can’t hold any more water. the reason you feel hotter in humid temperatures is because it’s more difficult for sweat to cool you down because the air is already pretty saturated with water.