Fight the dictatorship of relativism!

Many weather reports include a notation of the relative humidity, which reflects the fact that air’s capacity for holding moisture increases proportionally to the temperature of the air. Very few folks even know there us such a thing as absolute humidity, let alone what the measures of it would mean.

There is, though, a measure that’s less relative but still easy to grasp: the dewpoint.

The dewpoint is the temperature that must be attained for water to start condensing out of the air with no change to the absolute humidity.

This report includes both relative humidity and dewpoint. When I pulled it the relative humidity at the nearest station was 11% at a toasty 76 degrees F. The dewpoint was 18 degrees F.

Simple scale for determining whether the weather is too dry, too muggy or just right.

If the dewpoint is below 5, it’s dry enough to cause significant inconvenience. Be careful or you’ll get dry skin and perhaps nosebleeds.

If the dewpoint is between 6 and 15, you’ll need to drink lots of water.

If the dewpoint is between 16 and 25, it’s just about perfect.

If the dewpoint is between 26 and 35, it’s a little muggy, but not too much to bear.

If the dewpoint is between 36 and 50, air becomes noticeably heavy and activity becomes increasingly strenuous.

If the dewpoint is above 50, you’re in a location better suited to amphibians than to people.

NB, when the dewpoint is below 32 and the air cools to the dewpoint, you’ll get frost rather than dew.