Relative humidity compares the actual moisture in the air to:

Relative humidity is a measure that expresses the amount of moisture present in the air relative to the maximum amount of moisture that the air can hold at a specified temperature. This concept is crucial because warm air can hold more moisture than cooler air. Therefore, relative humidity provides insight into how close the air is to being saturated with moisture.

At 100% relative humidity, the air is fully saturated, which can lead to precipitation, but relative humidity below 100% indicates a dryer condition. By comparing the actual moisture in the air to the maximum capacity at that temperature, relative humidity helps gauge comfort levels, weather conditions, and potential for condensation. Understanding this relationship is essential in fields like meteorology and aviation, where managing moisture levels can impact safety and performance.