Frost on September pumpkins a possibility

It’s almost hard to believe that about a month ago, we were talking about very hot weather in North Idaho and surrounding regions.

For the summer of 2021, there were 44 days with high temperatures at or above 90 degrees at Cliff’s station in Coeur d’Alene. That includes seven days with readings at or above 100 degrees.

The hottest summer day was on June 29 with a record 107 degrees. The Coeur d’Alene Airport hit 109 degrees on that day, tying its all-time record.

At Spokane International Airport, there were 42 days with high temperatures at or above the 90-degree mark. Their highest reading was also on June 29, with an all-time record high of 109 degrees.

The two-month period from June 20 through Aug. 15 was the hottest in recorded history. Our average temperature in Coeur d’Alene was 91.9 degrees, compared to the average of 83.1 degrees. Since Aug. 16, our average high has dropped to slightly under 76 degrees, a big change indeed.

Late last week, low temperatures dipped into the mid-to-upper 30s in the outlying areas of Coeur d’Alene. At Cliff’s station, a chilly 42-degree reading was measured last Wednesday morning.

As we’ve been saying for many weeks, seasonal weather patterns in the Northwest seem to be coming early. Over the last several years, there have been early snows and early summers. Therefore, it’s not unlikely that we may be seeing early freezes develop across the North Country, especially toward the middle of the month.

The latest long-range forecast models, combined with our lunar cycles, are pointing to a very chilly weather pattern toward the end of next week. Freezing temperatures are expected in the higher elevations and perhaps down into the lower elevations as well, especially in the outlying areas.

Based on Cliff’s records dating back to 1895, the lowest temperature in Coeur d’Alene in September was 17 degrees, which occurred on Sept. 24, 1926. The following morning, the low was 22 degrees.

Also, that chilly period had measurable snow as an inch fell on Sept. 23, 1926. In 2019, we had measurable snowfall in Coeur d’Alene on Sept. 28 and 29 that totaled 1.1 inches.

Since 2000, there was a September freeze in Coeur d’Alene on Sept. 24, 2005. The morning low on that date was 32 degrees.

In 2019, we had two days with lows at or below the freezing mark. They occurred on Sept. 28 with a low of 32 degrees. The following morning, the low was 31.

Since 1895, the average date for the first freeze in Coeur d’Alene is around Oct. 16. The coldest reading ever recorded for October occurred on Oct. 31, 1935, with a low of 8 degrees.

More recently, the chilliest temperature was 19 degrees on Oct. 9, 2009. It was 20 degrees on Oct. 10, 2009. Two days later, the mercury dipped to a frigid 15 degrees. That was one of the worst early October cold waves to hit the region in history.

In terms of precipitation, the Inland Northwest continues to be very dry. Most stations had another below-normal month for rainfall in August. However, thanks to a thunderstorm, the August precipitation total at Cliff’s station was 1.37 inches, slightly above the normal of 1.23 inches. Had it not been for that single rain event, Coeur d’Alene would have seen its sixth month in a row with below-normal precipitation.

At Spokane International Airport, only .15 inches of rain fell last month. Its August normal is .47 inches. Since Jan. 1, only 5.03 inches of moisture has been measured at the airport, which is less than 50 percent of normal.

Other locations in eastern Washington have reported much-below-normal moisture as well. For example, Moses Lake has seen only 1.81 inches of rain since the beginning of the year, which is around 36 percent of normal.

This week, and most of next week, looks dry across the Inland Empire. Around the middle of the month, the strong high-pressure system is expected to weaken and allow some moisture into the region.

With these extreme weather patterns, when we have extremely dry conditions on one side, based on historical weather patterns, we will often flip to the wetter side. Therefore, our chances for wetter-than-normal weather become much higher in October and/or November.

For 2021, we think November will be a good one for moisture. It’s possible the wet weather could start in October, but these patterns will often take more time to develop.

Regardless, Coeur d’Alene could receive at least 11 inches of moisture for the fall season, or about 170 percent of normal, especially if a new cooler-than-normal sea-surface temperature event, La Nina, starts forming late this year.

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Contact Randy Mann at randy@longrangeweather.com