Does a dry spring also mean a dry summer?

Since the middle of May, temperatures have been relatively mild to warm in Coeur d’Alene and across the Inland Northwest. Highs were mostly in the 60s in early June with normal highs around the lower 70s. However, readings warmed into the 80s late last week. The previous warm spell was from May 10-12 with readings in the low 80s across the lower elevations of the Inland Northwest.

Most of our spring seasons have been wetter than normal over the last 20 years. Using the spring meteorological months of March, April and May, Coeur d’Alene has been approximately 125% of normal. For those three months, the normal precipitation in Coeur d’Alene is 6.08 inches. For 2024, the March through May spring total was lower than average as only 5.04 inches of rain fell at Cliff’s station. The system of meteorological seasons makes it easier for scientists and forecasters to calculate monthly and seasonal statistics. They were created for observing and forecasting weather patterns, which has proven useful for agriculture, commerce and other purposes.

Last March was a wet month as 2.43 inches of rain was reported, compared to the normal of 1.94 inches. April was very dry as a mere 0.39 inches of rain fell, much below the average of 1.77 inches. May’s rainfall was better with a total of 2.02 inches, just slightly below the normal of 2.37 inches. A large portion of the moisture this spring fell during two separate storms last month. On May 5-6, Coeur d’Alene had 0.77 inches with 0.93 inches falling May 22-23.

Conditions across the Inland Northwest were looking very dry despite the increased rainfall last month. However, in early June, a strong storm dumped 1.11 inches in Coeur d’Alene. Rainfall totals from the early June system were impressive in some of the outlying areas as well. For example, 1.63 inches fell at Hayden. About 1.50 was reported at Rathdrum with around 1.40 inches at Post Falls. Coeur d’Alene’s June average rainfall total is 1.93 inches, so there’s a decent chance that we’ll have a June precipitation total that is near to above average.

Despite the much-needed moisture to ease potential drought conditions, snowpacks in the higher mountains have been reported to be below normal levels. In March, snowpack levels were some of the lowest in Idaho in decades.

With the recent trend of mild temperatures over the last several weeks, 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 22 years, the upcoming summer season may be slightly drier than normal, but not as dry as 2023 when only 2.93 inches fell from June through August. This outlook is based upon the transition of sea-surface temperatures from the once warmer El Niño to the expected cooler La Niña later this year. Currently, we are in the in-between El Niño and La Niña which we call a “La Nada” pattern.

Many of the long-range computer models and sea-surface temperature forecasters are predicting that we are not expected to remain in a La Nada pattern for very long. Many of the international climate models are indicating the return of the cooler La Niña as early as the fall season. The latest information does show a thin line of sea-surface temperatures near the West Coast of South America and along the Equator below average levels.

If a new La Niña manages to form later this year, it would be the fourth one within the last five years. According to historical records, there have never been three La Niña events, followed by an El Niño, and then the formation of another La Niña in a short period of time.

Our wettest March through June spring season over the last 20 years occurred in 2017 with a whopping 13.83 inches, and this occurred during a weak La Niña event. In second place, the total was 13.09 inches for the three months in 2012, also a La Niña. 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.

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 Niña and warmer El Niño. Both years had moisture totals of approximately 1.5 times the summer average.

This week’s weather is expected to be dry across the Inland Northwest. Toward the middle of next week, the long-range computer models are indicating that a Pacific storm may bring the treat of some showers and thunderstorms to the region.

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Contact Randy Mann at randy@longrangeweather.com.