Is a measure of how much water an air mass at a given temperature can hold.
relative humidity
cloud cover
barometric pressure
all of the above

relative humidity is a measure of how much water an air mass at a given temperature can hold.

Explanation:

When a quantity of air at a supplied temperature exists the highest volume of water vapor, the air is considered to be saturated. The relative humidity is the water-vapor content of the air corresponding to its content at fullness.

Relative humidity can be described as the quantity of water vapor in air at a provided temperature related to what that air could endure at that temperature. We can thus adjust the relative humidity of an air bundle by either raising or lowering the volume of water vapor in the parcel OR by boosting or reducing the temperature of the air mass.