relative humidity

noun

1. the amount of water vapor in the air, expressed as a percentage of the maximum amount that the air could hold at the given temperature; the ratio of the actual water vapor pressure to the saturation vapor pressure. : RH, rh

relative humidity

noun

1. the mass of water vapour present in the air expressed as a percentage of the mass that would be present in an equal volume of saturated air at the same temperature Compare absolute humidity

relative humidity

1. The ratio of the actual amount of water vapor present in a volume of air at a given temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. Warm air can hold more water vapor than cool air, so a particular amount of water vapor will yield a lower relative humidity in warm air than it does in cool air.
2. Compare absolute humidity

Word History and Origins

Origin of relative humidity¹

First recorded in 1810–20

Example Sentences

The relative humidity proved the key factor affecting the reactor performance.

From Science Daily

On Saturday, the weather was cooperating with some 3,000 fire personnel working the blaze — as the winds died down and relative humidity levels rose.

From Los Angeles Times

The Santa Anas often bring triple-digit temperatures and a relative humidity below 10%, leading to drier fuel that can ignite more easily.

From Los Angeles Times

Those high winds coupled with low relative humidity, “will support rapid fire growth and erratic fire behavior,” the warning said.

From Los Angeles Times

“Highs will reach the lower 100s today while the minimum relative humidity will dip to the lower to mid-teens. Winds could gust to the near 20mph range in the afternoon.”

From Los Angeles Times