relative humidity

American  

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

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relative humidity British  

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

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relative humidity Scientific  

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

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Etymology

Origin of relative humidity

First recorded in 1810–20

Compare meaning

How does relative-humidity compare to similar and commonly confused words? Explore the most common comparisons:

• relative humidity vs. absolute humidity
• specific humidity vs. relative humidity

Example Sentences

These included educational attainment, median household income, racial composition, average temperature and relative humidity, smoking prevalence, BMI, and distance to the nearest hospital.

From Science Daily • Feb. 24, 2026

“The temperature drops and the relative humidity goes up, the winds die down, flames drop to the ground and it starts creeping along,” Hanson said.

From Los Angeles Times • Dec. 28, 2025

Temperatures dipped and relative humidity climbed, offering the possibility of a tamer fire to battle.

From Los Angeles Times • Sep. 8, 2025

Meteorologists in the US and elsewhere have expressed concerns over "reduced number of weather balloons" that observe wind, relative humidity and pressure above the ground.

From BBC • Jul. 6, 2025

Thus, the rainforests of the isthmus are characterized by a much higher relative humidity than are the savannas or semi-arid scrub forests.

From A Distributional Study of the Amphibians of the Isthmus of Tehuantepec, Mexico by Duellman, William E.