Even though we are still experiencing summerlike weather, fall has officially begun, so this is a good time to look back at our summer outlook, which covered the months of June, July and August.
In short, our outlook was awful, our worst ever. Here is what we got right (almost nothing) and what we got wrong (almost everything).
We predicted summer temperatures to end up about a degree below average — marking the first cooler-than-normal summer since 2009. This was a bust: The summer finished 1.8 degrees above average and ranked among the top 10 hottest on record.
Our individual monthly temperature predictions were also really bad. We predicted June to be around 1 degree below average, and it finished at 1.2 degrees above average. For July, we predicted temperatures around average, and the month finished 2.3 degrees above average. We predicted August to be 1 degree below average, and it ended up 2 degrees above average.
We place slightly less emphasis on precipitation, but in that area we did okay, predicting somewhat above average precipitation, and the summer total was actually 120 percent of average. However, the rain shut down after the first half of July.
We did make one spot-on prediction: We said there would be zero 100-degree days, and there weren’t any, although we did hit 99.
However, perhaps our worst prediction was the forecast for the number of days at or above 90 degrees. We called for just 15 to 20 between June and August, and we ended up with 47, which is well above the three-month average of 31. Additionally, we predicted that our longest 90-degree streak would reach five days, well short of the 12-day stretch we endured in mid-July.
In conclusion, since our temperature forecasts were more or less wrong across the board, we grade our summer outlook an F. We failed.
The main reason our forecast was off the mark was that El Niño, which tends to have a cooling influence on our summers, faded away during the second half of June and was all but gone by July. We had expected the El Niño influence to persist through the summer, holding back temperatures like it did in 2004 and 2009.
The loss of El Niño also reduced Pacific typhoon activity, especially during the second half of the summer. When there’s more typhoon activity, it tends to cause a rise in the jet stream over western North America and a dip in the East, which draws down cooler air. That did not happen.
While our overall summer outlook was a disaster, we should note that the month-ahead outlooks we issued for June, July and August were more or less on the mark, all predicting above-normal temperatures.
It’s also worth pointing out that despite this year’s hiccup, our summer outlooks have a very strong track record. From 2013 to 2018, we had accurately predicted summer conditions without exception. Of course, there’s the saying: “You’re only as good as your last forecast.”
A major takeaway from this summer forecast fiasco is that it is becoming exceptionally rare for Washington to have cooler-than-normal summers anymore. This was the 10th summer in a row with warmer-than-normal temperatures. With climate change, the odds are simply stacked against cool summers, and it raises the question whether they should be predicted anymore.
Hopefully we can redeem ourselves with our winter outlook, coming later this fall.
Past summer outlooks and evaluations
CWG’s 2018 summer outlook (We did not evaluate this outlook, but we did well calling for the summer to average one degree above normal, and it ended up two degrees above normal. In addition, we projected 35 days at or above 90 between June and August, which was the exact number.)
Matt Rogers contributed to this report.