Relative humidity facts for kids
Relative humidity is a way to describe how much water vapor (water in gas form) is in the air, compared to the most water vapor the air could possibly hold at that temperature. Think of it like a sponge: relative humidity tells you how full the sponge is with water.
Meteorologists, who are scientists who study the weather, often use relative humidity to understand and describe weather conditions in different places.
What is Relative Humidity?
When the temperature is warm, the air can hold more water vapor than when it is cold. Relative humidity compares the actual amount of water vapor in the air to the total amount it could hold. This comparison helps us know if the air feels dry or moist.
The value of relative humidity is usually shown as a percent.
- 0% means the air is completely dry. There is no water vapor in it.
- 100% means the air is completely full of water vapor. It is so moist that mist or dew is about to form.
How Temperature Affects Humidity
Imagine a warm room and a cold room. The air in the warm room can hold much more water vapor than the air in the cold room. This is why relative humidity changes with temperature, even if the actual amount of water vapor stays the same.
For example, if you have a certain amount of water vapor in the air, and the temperature drops, the relative humidity will go up. This is because the air can now hold less water vapor, so the existing amount takes up a larger percentage of its capacity.
What Happens When Air Cools Down?
When the air cools down a lot, especially if it's already holding a lot of water vapor (high relative humidity), the water vapor starts to change back into liquid water or ice. This process is called condensation or precipitation.
You can see this happen as:
These forms of water appear when the air becomes saturated, meaning it reaches 100% relative humidity.
