The following article was written by Michael Fagin. Fagin is an operational meteorologist providing weather forecasts to clients in the Pacific Northwest and providing custom forecast for groups climbing Mt. Everest and other major peaks. Fagin is also a travel writer with a focus on weather and wine. Read other articles by Fagin here. 

In our most recent update, we discussed weather conditions in the Pacific Northwest through mid-July. Here, we look at recent temperature and precipitation trends in Columbia Valley and Willamette Valley, drought conditions, and what the forecast La Niña might mean for the Pacific Northwest this winter.

Recent temperature trends

Let’s start by looking at conditions since our last analysis. We’ll focus first on temperatures from July 15^th until the end of meteorologist summer on August 30^th.

The map below is for the Tri-Cities Area, WA (NOAA is the source). Temperatures were generally a mixed bag of some periods slightly above average to slightly below average and others close to average much of the time. The blue bars are observations. Brown colors represent the average temperature range. Record heat is the red line above and record cold is the blue line below. One clear message is there was no record heat during this time.

The next map covers the Willamette Valley and Salem area. This region exhibited a similar mixed bag of temperatures as the Tri-Cities, but with slightly warmer temperatures at times. Also, there was one record heat day.

For the start of Fall, September temperatures for the Tri-Cities were generally above average. In the middle of the month, temperatures were below average and then moved back to above average.

For September, the Willamette Valley and Salem areas had a similar pattern to the Tri-Cities.

Growing Degree Days (GDD), a measure of heat accumulation, for the Tri-Cities through October 7^th are slightly above average, represented in the map below (from NOAA). The green line reflects this year and the brown line the average. (GDD is the cumulative average temperature over 50 F from April 1^st to October 31^st.)

The Willamette Valley and Salem area have a similar, slightly above average GDD.

Finally, let us take a quick look at the temperatures for the first 12 days of October. The Tri-Cities had below average temperatures in the first week of the month and recently had above average temperatures. For the Willamette Valley and Salem areas, much of the first 12 days of October had above normal temperatures.

Recent precipitation trends

Precipitation for the Tri-Cities from our last data on July 15^th to October 7^th indicates that levels were below average. The map below has the current year totals in green. Average is the brown line.

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