What is relative humidity?

Relative humidity is defined as the ratio of the current amount of water vapor in the air to the maximum amount of water vapor the air can hold at a given temperature, expressed as a percentage. This measurement is crucial because warm air can hold more moisture than cold air; thus, relative humidity accounts for temperature when determining how close the air is to saturation.

As a result, at a specific temperature, a relative humidity of 100% indicates that the air is fully saturated with moisture, while lower percentages indicate lesser amounts relative to that maximum capacity. This concept helps meteorologists and scientists understand weather conditions and predict changes in the atmosphere, as high relative humidity can lead to phenomena such as fog or precipitation, while low relative humidity may lead to dry conditions.

The other options, while related to the presence of moisture, do not accurately convey this ratio in relation to atmospheric conditions.