Q: “Mike, we’ve had some single-digit humidity levels recently (my very dry hands can attest to it, along with your nightly reports on Channel 2). Is it possible to reach 0% humidity?”

The answer to that depends on whether you are speaking theoretically or practically. Theoretically speaking, the answer is yes. But from a practical standpoint, you’ll never see it.

Bone dry

Let’s start with theory. If you go into the laboratory, take a sample of air, and physically remove every molecule of water vapor (either by chemical or physical means), then you would be left with air that is by definition 100% unsaturated… or in other words, has a relative humidity of 0%.

But we don’t live in a lab, and there is always some water vapor present in the air. Oceans, lakes, rivers, and even plant life sees to that. Air, by its very nature, is somewhat self-regulating that way. The drier you make it, the more it wants to pull water molecules out of whatever source is available, including chapped hands. So natural weather processes will never result in a true relative humidity reading of 0%.