Precipitation During the Driest Time of the Year: But a Threat Exists

Rain is coming to western Washington and the Cascades during the climatologically driest time of the year.

But there is an accompanying risk that needs to be mentioned.

A winter-looking system is off our coast, including an impressive cold front (indicated by a red arrow) and a low center at the center of swirling clouds.

This impressive summer system is associated with a relatively strong upper-level trough, as shown by the 500 hPa heights (think pressure at 18,000 ft) tomorrow at 11 AM.

Not your typical mid-summer pattern 😊

Precipitation will move in on Saturday morning.   The predicted totals through 5 PM Saturday (shown below) will be most substantial on the windward sides of regional terrain (up to about .5 inches).  

Accompanied by cool air, this event should greatly reduce the potential for wildfires west of the Cascade crests for a week or so.    

Some light showers will continue into Sunday, but the totals through Monday morning will be only a bit more:

So far, good news.  Reduce westside fire potential and lessen water needs for days.

However, there is a risk factor that needs to be mentioned: increased surface westerly winds east of the Cascade crests, which are driven by the accumulated cool air over western Washington,as well as increased winds at crest level.

Consider the forecast wind gusts on Saturday afternoon.  Strong westerly winds from Yakima to Omak, with substantial gusts extending into the Columbia Basin.  Maybe even some gust storms.

Consider Camp 4 on Lake Chelan ( red dot below)

The predicted sustained winds by the UW modeling system at this location are substantial, with sustained winds reaching 20 kt or more.

The threat is that some of the fires in eastern WA could be enhanced and rapidly spread by these strong westerly winds on Saturday.  

 If you are located east of a current fire, great caution is advisable.

Has Eastern Washington Gotten Drier or Warmer?

 With the recent grass/range fires in Eastern Washington, there is some interest in whether conditions there have gotten drier or warmer.   

 How unusual have precipitation and temperature been this year?

Let's find out!

I will start with the NOAA Climate Division dataset, which is derived from multiple climate observation locations in each division (the climate division map for Washington State is shown below).  

For Division 8, on the eastern slopes of the Cascades, the history of summer precipitation and temperature since 1960 is shown below.

For precipitation, there is little long-term trend.

For temperature, there is a warming trend of about 0.2F per decade.  Some of that represents the global warming signal.

Moving to the lower-elevation Columbia Basin, there is again little overall trend in precipitation over the period, but there have been a few dry years in the past decade.

The temperature plot for that area shows warming, particularly during the past decade.  Some of that warming undoubtedly reflects the global warming signal (although land use changes, urbanization, and other factors are certainly significant as well). Same upward rate of 0.2 F per decade.

 What about this year?   

Here are the plots of precipitation and temperature at Ellensburg in eastern Washington for June 1 to July 28.

A small warming trend in temperatures, with this year not being extreme at all-- near the long-term mean.

For precipitation, there is a LOT of historical variability, with this year being relatively low (fifteenth lowest out of 67)

In short, conditions in eastern Washington have hardly been exceptional for the first half of summer 2026, with a very modest warming signal evident.  

This is why the fuel moistures were near normal.

The only reason we had significant grass fires was due to a huge amount of lightning, which has little to do with global warming.