Does a wet spring mean a dry summer?

We had our first good taste of summer last week as high temperatures climbed into the 80s in Coeur d’Alene and surrounding regions Thursday and Friday. Many stations came close to the 90-degree mark May 19 as Cliff reported a high of 88 degrees. This was one degree from tying the record for the date of 89 degrees set back in 1956.

However, many locations did manage to hit the 90-degree mark on Saturday for the first time this year. It was a record-breaking 91 degrees in Coeur d’Alene, breaking the old record of 88 degrees in 1958. It was 90 degrees at the Spokane International Airport. The last time it was this warm was Sept. 30, 2022, when the mercury hit 90 degrees in Coeur d’Alene.

With the recent warm to hot temperatures, many are wondering if this is a sign pointing to a potentially hot summer across the Inland Northwest. Based on the climatological records dating over the last 20 years, there is a good chance this upcoming summer season will be warmer and a little drier than average.

Since 2004, the majority of our spring seasons have been wetter than normal. Using the spring meteorological months of March, April and May, Coeur d’Alene has been approximately 129% of normal. For those three months, the normal precipitation in Coeur d’Alene is 6.08 inches. For 2023, the March through May 20 spring total is around 7-and-a-quarter inches with more moisture expected before May comes to an end.

Our wettest March through June spring season over the last 20 years occurred in 2017 with a whopping 13.83 inches. In second place, the total was 13.09 inches for the three months in 2012. This was also the same year that Coeur d’Alene reported its wettest year since 1895 with a whopping 43.27 inches of rain and melted snow.

Most of our very wet spring seasons have occurred when there has been a moderate La Niña event. As I’ve mentioned previously, La Niña is the abnormal cooling of sea-surface temperatures along the Equatorial regions westward to the west coast of South America. However, there was one instance of a dry spring season during a moderate La Niña. This occurred back in 2021 when only 2.80 inches of moisture fell.

Over the last 20 years, there have been only two moderate El Niño events during the spring season. The most recent was back in 2015 when Coeur d’Alene reported 6.02 inches of moisture, which was very close to normal. In 2009, during another El Niño, the spring season was wet with 8.35 inches of precipitation.

In terms of the “meteorological” summer seasons, they begin June 1 and end Aug. 31. The “astronomical” summer season begins June 21 and ends late Sept. 22. The normal precipitation for those three months is 4.08 inches. Within the last 20 years, the majority of our summer precipitation has been below normal, especially after the middle of June. Our wettest summer season occurred in 2012, the record year for moisture, with more than twice the normal of 8.68 inches. We also had some wet summer seasons in 2013 and 2014 when sea-surface temperature patterns were in a La Nada, the in-between cooler La Nina and warmer El Niño. Both years had moisture totals of approximately 1.5 times the summer average.

Currently, sea-surface temperatures are warming up to where scientists believe that a new El Niño will be declared later this year, perhaps as early as the late summer. Despite the fluctuations in sea-surface temperatures, we’ve had a drier-than-normal summer season from 2015 through 2021. Last year, the three-month period of June through August was wetter than average with a total of 5.87 inches. But, the majority of the moisture fell within the first two weeks of June with a total of 4.85 inches. Much of the summer was dry as not a drop of rain was seen from July 19 through Sept. 3.

For the upcoming summer season, we should see more storms move through the region through the early to mid portion of June. Once again, the late June through August period will likely be drier than average, but we don’t believe it will be quite as dry as last year.

In terms of our near-term weather, conditions will return to more springlike this week with occasional showers and isolated thunderstorms, along with cooler temperatures. In fact, as previously mentioned, the weather patterns for the northwestern U.S. will likely be unsettled into June with occasional showers and thunderstorms. After the hot Saturday, we don’t see any 90-degree temperatures until at least the middle of next month.

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Contact Randy Mann at randy@longrangeweather.com.