https://f451labs.com/filed/Recent content in Filed on F451 LabsHugoen-usSun, 31 May 2026 00:00:00 +0000https://f451labs.com/filed/relative-humidity-is-a-temperature-measurement/Sun, 31 May 2026 00:00:00 +0000https://f451labs.com/filed/relative-humidity-is-a-temperature-measurement/<p>Filed under best practices, because it is the kind of thing that is easy to get wrong and expensive to notice later.</p> <p>Relative humidity is not an independent quantity. It is the ratio of the water vapor actually present to the most the air could hold at that temperature, expressed as a percentage. The denominator — saturation vapor pressure — climbs steeply with temperature: roughly <code>7%</code> per <code>°C</code> near room temperature. So the same absolute amount of water in the air reads as a different RH at <code>20°C</code> than at <code>25°C</code>. A relative humidity figure without the temperature it was measured at is half a reading.</p>