Tuesday, June 29, 2010

Rain Rain Come Today!

Rain rain come today!
Come and rain on every day!

It was 108 yesterday...109 day before that (about 43 C. for you metricians).  Sunny and hot.  The last time we had measurable rain was May 2nd.  Sad part is, this is perfectly normal for us in late June.  Dry heat...whatever. That's just plain hot.

117 is the record: June 24 1989.  I drove to Phoenix that day...where it was 122...in my old Corolla...with no A/C.  The next day we went toobin' on the Salt River, where I learned a very painful lesson about sunscreen.  Only time I ever blistered...ouch!  Oh, I had fun, but young and careless has consequences.

Tucson sits on the cusp of being defined as a desert, averaging 11 inches of rain a year, with an inch or two of snow the odd year out (a light dusting in our driveway is shown above).   Indeed, suprisingly verdant landscapes can be found just a few miles to the south and east of Tucson, where the elevation is higher and the rainfall greater.  We also have all these mountains...six ranges in southeast Arizona that rise over 9000 feet.  Sky islands, we call them.  The isolated forests at the top are comparable to those of the Canadian Rockies.

We've got two rainy seasons.  The quieter winter storms, usually in February and March, provide the desert plants with a lot of essential moisture...soaking in slowly while it's not blazing hot.  This last winter we got over 7" at our house!  Then it's the booming monsoon season, usually starting (we hope) in early July and fizzling out in September.  Temperatures go down a few degrees but the humidity goes up, so unless it actually does rain, it can be pretty relentless...as occured last year when most of the city got ripped off for our annual lightning show and thunderstorms that can drop two inches of rain in an hour.  (Our measured record at the house is 2.75" in one 24 hour period...a quarter of our annual rainfall!)  The few summers before the last, we fared average or better.  It's goes into a blur before that but I've seen quite a variety.  The summers of '89 and '90 (I think) when we had some 39 days in a row over 100 degrees...but years later, a summer when we had a similar streak of days under 100 degrees!

The tree with Kirsteen at left is on Mount Graham and had recently been struck by lightning, ripping a line of bark all the way down the tree and sticking a 15-foot splinter solidly into the ground. Glad we weren't there when it happened!  The lightning shot above is about the best I've ever managed on the fly...I really need to make a go of getting some decent shots this summer.  Lower right is a storm cell crossing the Aravaipa Valley seen from a high perch on Mount Graham.

On top of seasonal variations, we've got some longer cycles in the desert.  El Niño and La Niña play havoc with our year-to-year rainfall amounts.  El Niño often brings us more winter rain and those spectacular spring wildflower shows.  La Niña gives us those long mild dry winters for which we are the envy of others living in colder climes.  Not enough El Niño and the desert will show it bad after a few years or so...then it rains more and everything goes back to happy.  For where I've been getting around lately, the deserts have been pretty happy.  Here's crossing our fingers for this season; predictions are for better than average.

What might appear as autumn foliage is actually a stress reaction by southern Arizona live oak trees...this is springtime after a winter with almost no rain.

This is springtime with an abundance of rain. First a carpet of wildflowers in the remote Vekol Valley...the second is a well-known location a few miles beyond Kitt Peak Junction.

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