How Unusual Was This Summer?

 Today is the last day of summer, so it is a good time to evaluate what happened the past three months.

Let's start with the average daily temperature.  Below is the deviation of daily temperatures from normal for the western US.

Cooler than normal over much of California and southern Nevada, but warmer than normal over Washington and western Oregon--by around 2-4°F.

For precipitation, much of California and eastern Oregon were wetter than normal, while most of Washington was drier than normal by a few inches.

Let's take a closer look on how unusual this summer was by looking at a few local observing locations.

Starting with the June 21- September 20 observations at Olympia, WA. from the late 1940s to this summer,  we note a slot increase by around 3°F over the period, with this year being warmer than normal but not record breaking.

Interestingly, the high temperatures this summer were very typical, with only a slight long-term trend in heatwave temperatures.

This is something the media has not been noting....the warmest temperatures are not rising much.  The big warm-up is in the lowest temperatures each day.

 

For precipitation (below), we see a slow drying trend in a region-- a region that does not get much rain over the summer.  This summer was drier than normal, but not nearly the driest.

Now let's turn to Moses Lake in the Columbia Basin of eastern Washington.  Clear warning trend, and this summer was the warmest on record.  

Precipitation as Moses Lake?   Modest drying over the years.

As shown above, general warmth and dryness this summer was not universal over the western US and mainly over Washingon State and western Oregon.

Why you ask? 

 Because a persistent upper-level pattern developed, with higher pressure/heights over southwest Canada (red colors below) and lower heights/pressure over California.  High pressure is associated with sinking air, producing warmer and drier than normal conditions.

Why was this pattern so persistent?   I cannot tell you for sure.

Finally, how good was the seasonal forecast by the National Weather Service made before the summer started?  As shown below, not that great....got the warmth over the NW but missed the cooling over the southwest.

Temperatures will warm up during the next few days, but nothing serious over western WA--mid to upper 70s at most.  

Enjoy is while you can.  In one month, we will be entering the murk of Northwest winter.