Monday, September 19, 2011

September in the Sonoran Desert

September is one of the more quiet months in the desert.  With heat dropping, things feel a little more relaxing.  Their aren't a lot of really exciting things going on in the desert, but to the person who looks closely there are all kinds of subtleties happening.

September in the Sonoran Desert means the end of monsoon season.  Usually, the month begins with the waning of monsoons and higher humidity.  Later in the month however, humidity drops and the rains end.  Humidity has dropped from dew points in the 50's to the 30's this past weekend.  Temperatures are also dipping into the 90's for highs which is very good news.  Effects from the scant rainfall continue to linger in the desert.  We will have left over mosquitoes and gnats that hatched during the rain we received earlier in September for the next few weeks or so.  There typically are more than the usual butterflies out starting in September also.  Fall bird migration is also just beginning in the desert.  I have already seen a few hawks migrating through the area.  Cacti are also slightly more plump from the rainfall their roots absorbed and stored in their stem tissue.  Other plants such as Occotillos still have their leafs, which will likely only last a few weeks or so.

Monsoon season is also one of the times of year that dry washes run with short lived flash floods.  Unfortunately, this year the rains were far too scant so only washes with an abundance of bedrock in their channels ran.  Fortunately, their was enough rain in most locations to refill some of the water holes in the mountains, which desert wildlife is extremely grateful for.  These waterholes should get a lot of desert animals through the next several months or so.  September does mark the beginning of the Sonoran Deserts second annual seasonal drought.  The most intense annual drought occurs from late April through early July.  After monsoon season a much less intense and less consistent annual drought occurs from late September through late November.  Temperatures continue to drop during this time, humidity is usually slightly higher (but not nearly as high as monsoon season), and rain does happen on occasion during this second drought.  This all makes desert life much more bearable.

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