Great question Sherri. Humidity is a quantity representing the amount of water vapor in the atmosphere or a gas.
The more humid it is, the more moisture there is in the air, and that can lead to a better chance of rain and storms.
Humidity is relative to the temperature. Humidity is highest when the air is at it's coolest. The reason is cool air cannot hold as much moisture, and so the air condenses quicker which leads to higher humidity, resulting in more clouds and fog.
Conversely, warmer air can hold more moisture, and it takes much longer to become saturated. So, humidity values will typically be at their lowest each afternoon.