Thursday, September 1, 2016

Just How Dry Was This Summer?

Last night I awoke with a start to drops hitting the roof and leaves rustling on the windows.  My heart raced in anticipation of rainfall.  Alas, it wasn't to be.  A few sprinkles, some gusty winds, and it was over.

Similarly, this morning teased us with an ominous sky, virga, and even some mammatus clouds.

As I walked to the bus, I briefly felt raindrops on my face and arms.  So exciting!  However, hopes were once again dashed as the system moved off to the northeast.

Just how dry has it been this summer?  Well, August 31 is in the books and we can now take a look back at all of meteorological summer (June, July, and August).  Total rainfall at the Salt Lake City airport was 0.67", making it the 11th driest all time.

To put that into perspective, the histogram below shows the amount of precipitation falling in Salt Lake City by year back to 1874 ordered from high to low (I've left the years off since there are so many).  2016 is highlighted in red.  Yes, there have been drier summers, but the amount of water in the rain bucket this year is quite low and in the 10% driest summers.

For temperature, we fell just shy of the hottest of all time (behind 2013), but ended up 2nd and a full degree warmer than the next highest summer, 2007.

Source: NOAA Regional Climate Centers
You put that combination of little precipitation and exceptional warmth together and you probably have the "driest" summer on record in Salt Lake, or at least something that is close to that, if you think about it from the perspective of precipitation minus evaporation.

In the foothills, most of the grasses turn brown during the summer, but this year one sees gamble oak and other species highly stressed with browning leaves.  Near the mouth of Dry Creek just northeast of campus, where most plants survive for the summer, everything appears to be dead.

Although we may get lucky with a shower or thunderstorm today (or unlucky if it happens during the football game), we need things to turn around quickly or we are going to be entering the cool season with a huge deficit in soil moisture.   If we have a big snow season (wouldn't that be grand), that won't be a problem, but if we have another meager year, it will cut into the runoff as the first "reservoir" to be filled when the snow starts to melt is the soil.

At least cooler weather is on the way.  Looking forward to it.


Plot of summer precipitation @KSLC chronologically by year added below at request of commenter.


  1. It is interesting to compare your graphics here; while the temperature chart is arranged chronologically, the precipitation chart is not. What is so telling of course is that the summertime temperatures have clearly been increasing over time. Could you whip out a quick chronological illustration of annual summer precipitation numbers, so that we can visualize precipitation trends over time?

    1. Added as an addendum at the end of the post.

    2. Jim,

      Thanks for the extra graph; we'll see what happens next!

  2. As often the case, most of what fell at SLC for this period was during one or two fairly localized convective storms in June. In this case I think many other portions of northern UT are even drier compared to normal... for example the far north, and portions of the Wasatch and Uintas. I noticed on the NWS site that Evanston, WY for example is less than half the normal for the calendar year (3.87 so far) and only 0.47 forJun-Aug (which compares to a Jun-Aug average of 3.10", slightly higher there than that for SLC).

  3. I don't have any data, but it sure seemed dry (relative) in Ketchikan June, July, and August. Just started raining in earnest now.

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