Determines how much water vapor an air mass will hold?

The amount of water vapor an air mass can hold is primarily determined by its temperature and pressure, following the principles of the Clausius-Clapeyron relationship. Warmer air can hold more moisture, while cooler air holds less. Additionally, humidity levels indicate how saturated the air is with water vapor, which is influenced by temperature and the presence of water sources. Thus, the capacity for water vapor in an air mass increases with rising temperatures.