What is humidity anyway?
Water comes in three forms: liquid, vapor, and ice. The definition of water vapor is gas that mingles with
air. So, humidity is the amount of water vapor in the air. We call this relative humidity
There is a percentage which indicates to us the amount of moisture in the air relative to the maximum amount the
air can hold at a certain temperature.
For example, at a certain temperature when the air contains all the water vapor it can hold, it has a relative
humidity of 100%. If humidity exceeds 100% moisture will begin to condense from the air. So if the
air contains only half the water it can hold at a certain temperature, the relative humidity would be 50%.
Here's a snapshot I took of my little weather station showing indoor and outdoor temp and humidity.