Can the dew point in the high desert drop below zero?
Our niece lives in the California high desert and the dew point there was listed as minus 6. Could this be accurate?
William Girard, Shorewood
It is accurate and that reading is a testament as to how dry the desert can get. The dew point can drop below zero in the same manner that the temperature can. Dew point is the temperature to which air must be cooled for saturation to occur, so in your example, the temperature would have to fall to 6 below zero for condensation to occur. Because the dew point can never be higher than the temperature, by definition there must be a negative dew point any time the temperature is below zero. Chicago’s lowest dew points have approached 40 below, occurring on a few occasions during the brutally cold winters of the early and mid-1980s when city temperatures dropped to as low as minus 27.
The dew point can drop below zero in the same manner that the temperature can.