Humidity In The Desert

Texas sage

9/24/11

     As I mentioned in my last post, so many plants that had been dormant for weeks in the summer heat have started blooming again now that we are having "cooler" weather.  My Texas sage bushes have all burst into bloom this week.  And the Red Bird of Paradise bushes (also known as Pride of Barbados) suddenly have many more and brighter blooms instead of an anemic few.

     But another way I can tell fall is on its way here in the desert southwest is that my skin is becoming very dry and starting to itch because dew points and humidity are rapidly falling.  Until I moved here, I never knew that there was any humidity in the desert.  But when the monsoon season starts here in mid June, dew points begin to rise into the 50's.  Humidity from the moist southerly winds routinely will be in the 30 to 60 percent range.Both are a welcome relief from the parching dryness.

Mexican Bird of Paradise

     In the fall, winter, and spring here humidity runs from 2 to 12 percent, and dew points plunge.  I never knew that minus dew point temperatures  existed.  However, in the winter here, with single digit humidity, minus dew points occur.  I have seen a dew point temperature as low as -34  last winter.  The concept of moisture in the atmosphere, how it is measured, and how it changes is fairly complex.  As I understand it, dew point is the Fahrenheit measure of humidity (the absolute measure of water vapor in the air).  So if the Fahrenheit (or absolute) measure of humidity is in the minus column (below zero), you can imagine how dry that feels.  It can feel cold even if the temperature is 60 degrees F (16 C).


     Just this week dew points have fallen from the 50's to the mid 30's.  And we've had a few days where the humidity has fallen into the single digits.  So bring out the heavy duty moisture creams, and if this fails to take away the itch, grab the benadryl cream.