RANDY MANN: It's almost autumn - and Indian summer is here

Our warm and dry weather pattern was briefly interrupted by welcome rain across the Inland Northwest over the weekend. Despite the recent moisture, the long-range computer models are showing the rest of September to be dry and warm.

As of this Saturday writing, it appears that September will be another month in 2021 with below-normal precipitation. The normal rainfall for this month is 1.48 inches.

Around the beginning of October, we should start to see an increase of moisture once again across the Inland Empire.

Late last week, low temperatures dipped into the low-to-mid-30s in the outlying areas of Coeur d’Alene. At Cliff’s station, a chilly 39-degree reading was measured last Thursday 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.

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.

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.

Last year in September, morning low temperatures stayed well above the freezing mark. 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.

Our first day below freezing in October 2020 happened on Oct. 22 with a low of 27 degrees. That frigid air mass last year kept our daily high temperatures below freezing with highs near 30 degrees from Oct. 24-26. Those three days were records for low-maximum temperatures.

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.

We should see morning low temperatures challenge the freezing mark in Coeur d’Alene in early to mid-October.

Speaking of cold, parts of the Southern Hemisphere experienced some very cold weather during their recent winter season, which is our summer. For example, there were several hard freezes in southern Brazil in July that damaged coffee and orange trees. Other cold-sensitive crops were also damaged due to the unusual conditions.

Also, in late July, rare snows blanketed the lower elevations of the Brazilian state of Rio Grande do Sul. It had been about 10 years since snow had fallen in lower elevations. However, snow in June, July and August is very common in the mountain areas in that part of the world.

The cold weather in the Southern Hemisphere over the last three months has also led to a super-sized ozone hole over Antarctica. According to the European Union’s Copernicus Atmosphere Monitoring Service, this was the second year in a row with a large ozone hole forming over the South Pole at this time of year. By contrast, the same region had its smallest ozone hole two years ago since measurements began in 1979.

The ozone layer in our upper atmosphere protects us from harmful ultraviolet radiation that can lead to skin cancer. It typically reaches its largest size from August through October. Typically, by late in the year as temperatures warm up in the Southern Hemisphere, the ozone layer returns to normal.

This year’s depletion, which is bigger than Antarctica itself, is mostly due to the chlorofluorocarbons (CFCs), toxic chemicals used for aerosol sprays and refrigerants. The use of these chemicals has been reduced considerably since the late 20th century as the ozone hole is expected to slowly recover and hopefully return to its normal cycle around the middle of this century.

Despite the chilly weather in the Southern Hemisphere, it was the exact opposite in the Northern Hemisphere. According to the National Oceanic and Atmospheric Administration, the June through August period in the U.S. was the hottest in history. It barely beat out the Dust Bowl year of 1936 by 0.01 degrees. The average temperature was 74 degrees Fahrenheit, which was about 2.6 degrees warmer than the long-term average.

NOAA said the Northern Hemisphere had the hottest July and second hottest June in recorded history. Much of the incredible heat was felt in the West this summer. Portland had a record 116 degrees and Salem, Ore., hit 117 degrees in late June.

In early July, Death Valley, Calif., hit 130 degrees, very close to the all-time world record of 134 degrees set back in 1913. In Coeur d’Alene, we hit 107 degrees and Spokane International Airport hit an all-time record of 109 in late June.

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Contact Randy Mann at randy@longrangeweather.com