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

“With a low relative humidity and extreme temperatures, the fire environment will be capable of creating extreme fire behavior,” Cohen said.

From Los Angeles Times

Those conditions will be particularly challenging when combined with low relative humidity, little cooling at night and a dry landscape.

From Los Angeles Times

Those winds could be more concerning given otherwise hot and dry weather, with temperatures around the fire expected to reach into the low 90s Thursday, and relative humidity dropping to 20% or lower.

From Los Angeles Times

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

“A combination of strong winds, low relative humidity, and warm temperatures can contribute to extreme fire behavior,” the weather service warned of these areas.

From Los Angeles Times