What does relative humidity measure?

Relative humidity measures the amount of moisture in the air compared to the maximum amount of moisture that air can hold at a given temperature. This is crucial because the capacity of air to hold moisture increases with temperature. Therefore, relative humidity expresses how saturated the air is with water vapor, indicating how close the air is to being fully saturated.

When relative humidity is at 100%, the air is fully saturated, and any additional moisture can lead to condensation, such as dew or fog. In contrast, lower relative humidity values indicate drier air. Understanding relative humidity is essential for meteorology and weather forecasting, as it influences weather patterns, comfort levels, and the likelihood of precipitation.