Overall, fall was warmer and drier than average, owing to abnormally warm and dry weather across most of the area in September and October. In November the weather turned abruptly colder, and also wetter in some areas, notably the Upper Treasure Valley in Idaho and central Malheur County in Oregon.
September 2022
The upper level high pressure ridge which contributed to the second warmest summer on record remained over the western U.S. through most of September, maintaining the mostly dry and unusually warm weather.
On the 2nd and 3rd, a weak upper level low pressure trough pulled up warmer air from the south as it moved inland over Oregon, Washington, and northern Idaho, and several records were tied or broken.
date location record previous record
9/2 Boise 101 101 in 1950
Burns 102 100 in 1950
McCall 91 91 in 1945
9/3 Boise 102 101 in 1931
Ontario 101 99 in 1960
Twin Falls 99 98 in 2007
On the 4th and 5th, a second trough, kicked inland by a deep trough in the Gulf of Alaska, brought minor cooling to the Boise area as it crossed western Canada, but highs were still more than 10 degrees above normal.
On the 6th and 7th, the ridge produced more record heat as it expanded northward.
date location record previous record
9/6 Boise 101 98 in 1955
Burns 101 96 in 1955
McCall 95 91 in 1955
Jerome 102 101 in 1955
Twin Falls 102 90 in 1998
Baker City 99 94 in 1944
9/7 Boise 104 97 in 1955
Burns 98 95 in 2021
McCall 92 89 in 1920
Ontario 102 99 in 1967
Mt. Home 103 102 in 1955
Twin Falls 100 92 in 1998
It might have been even hotter had it not been for persistent wildfire smoke.
A pattern change ensued on the 7th as the trough in the Gulf of Alaska moved over the Canadian coast. The cold front ahead of the trough, plus hot surface temperatures, contributed to the development of strong thunderstorms with gusty outflow winds. Wind gusts exceeding 50 mph were common all over Harney and Malheur Counties. There was even a dust storm in Canyon County east of Greenleaf. The strongest measured wind gust was 78 mph near Rome.
By the 8th, the trough was over western Canada and the northwest U.S., and the ridge had shifted to off the northwest coast. Northwest flow plus a veil of smoke restricted high temperatures.
By the 10th, the ridge had drifted back over the Intermountain Region, but smoke prevented valley temperatures from rising above the 80s. The smoke had no effect on lows however.
A record low of 40 at Twin Falls on the 11th broke the previous record of 42 set in 2010.
By the 12th, the ridge axis had migrated far enough inland to allow southerly flow aloft to transport clouds from former hurricane Kay over our area.
On the 13th, a weak trough over the northwest coast interacting with the Kay moisture triggered isolated thunderstorms. Then on the 15th, the trough encouraged more thunderstorm development across our area.
By the 17th, another trough from the Gulf of Alaska had moved down the coast, strengthening the trough that was already in place. The resulting southerly flow caused a warming trend from the 18th through the 20th.
On the 20th, the trough began to move inland, setting off isolated strong thunderstorms. An outflow gust of 60 mph was measured at Burns that evening. On the 21st, gusts from 45 to 60 mph were common across southwest Idaho from midday through mid afternoon. A gust of 72 mph was measured 19 miles east-southeast of Riddle in Owyhee County.
The trough drifted directly over Idaho on the 22nd, bringing the coolest day of the month to many locations.
Temperatures warmed from the 23rd through the 27th as the ridge rebuilt over the Western Region, and more records were broken or tied.
date location record previous record
9/27 Boise 95 92 in 1957
Burns 92 91 in 1963
McCall 85 84 in 1949
Mountain Home 93 93 in 1963
Twin Falls 89 87 in 2010
9/28 Ontario 92 90 in 1963
A Pacific cold front crossed our area on the 29th, lowering temperatures to near normal.
The upper level trough following the front kept temperatures near normal on the last day of the month.
October 2022
The first three weeks of October were warm and dry. Temperatures were above normal every day except the 1st, averaging 5-10 degrees above normal for the period.
Except for the 30th and 31st, the rest of the month was relatively cool. There was enough rain to bring the month’s total to slightly above normal in Ada County and parts of Baker County, while the rest of our area had near or below normal precipitation .
Overall, October averaged a few degrees warmer than normal.
An upper level high pressure ridge was the dominating feature through the 19th. On the 20 th , strong westerly flow aloft succeeded in flattening the ridge. This allowed a cold upper level trough from the Gulf of Alaska to invade the northern Intermountain Region on the 22nd. On the 20th, just ahead of the cold front, Burns registered a record high of 79, breaking the previous record of 76 set in 2003.
Rain which began late on the 21st was the first measurable precipitation since September 21st at many locations. Most of it fell as the trough deepened over the region on the 22nd. By the time the rain ended, .84 inch had fallen at the Boise airport. The .67 inch which fell on the 22nd set a new record for the date.
Gusty west-northwest winds accompanied the colder air.
On the 24th and 26th, weak disturbances from the Gulf of Alaska brought light rain.
With the jet stream north of the Canadian border from the 27th through the 31st, our area enjoyed dry weather with a warming trend. On the 31st, ahead of an incoming major trough, southwest flow aloft and southeast winds at the surface pushed temperatures above normal, but no records were set.
November 2022
November 2022 was nearly as cold as the average December. And it was one of the wettest Novembers in some areas, including parts of the Treasure Valley and Malheur County.
The month started out “warm” on the 1st under strong southwest flow aloft in advance of a deep upper level trough. Following the trough’s cold front, much cooler weather ensued on the 2nd, setting the theme for the rest of the month.
As the trough exited to the east on the 4th, very moist northwest flow aloft dumped .55 inch of precipitation at the Boise airport, a new record for the date. That included .2 inch of snow, which tied the record for the date set in 2011. It was the first measurable snow of the season. A record rainfall of .36 inch was set at Baker, breaking their previous record of .3 inch set in 1990.
Precipitation tapered off on the 5th as milder Pacific air provided near normal temperatures through the 8th.
On the 5th and 6th, an upper level ridge between the west coast and Hawaii amplified northward toward the Aleutians, resulting in northerly flow aloft off the Canadian coast. An upper level trough in the Gulf of Alaska responded by moving south along the coast. It arrived over the Pacific Northwest on the 7th, bringing three days of wet weather.
Starting on the 9 th , an inversion kept valley temperatures much below normal through the 22nd. Periods of fog, low clouds, and haze plagued the area starting on the 16th.
On the 12th and 13th, a weak upper level trough crossed the Pacific Northwest and Great Basin. On the 14th an even weaker trough moved down the coast to California. These systems had no effect on our inversion and brought no precipitation.
On the 14th and 15th, a deep upper level trough between Hawaii and the Aleutians prompted an upper level ridge to build over the coast. The ridge kept a lid on the inversion through the 17th, preventing the stagnant air in the valleys from mixing out.
On the 18th, an upper level trough moving south out of Canada brought light snow. It also cleared the air by replacing the cold air under the inversion with cleaner air which was just as cold. The result was record cold at a few locations.
date location record previous record
11/10 Burns 1 4 in 1978
11/17 Burns -3 1 in 2014
11/18 McCall 1 2 in 2014
11/19 Twin Falls 7 10 in 2000
Burns -2 3 in 1994
11/21 Twin Falls 9 11 in 2018
On the 22nd, an eastward-moving trough brought snow, mostly falling in the mountains. It was followed by an upper level ridge and warmer Pacific air which replaced the cold air in the valley on the 23rd. Although the inversion was back by the morning of the 24th, temperatures from the 23rd through the 25th were the warmest since the 8th.
Early on the morning of the 26th, a Pacific cold front brought more snow, which again fell mostly in the mountains. Low clouds and dense morning fog followed the front.
On the 26th and 27th, an upper level ridge again amplified between Hawaii and the Aleutians, putting our area under northwest flow aloft from Alaska.
At the same time, a deep and very cold upper level trough from Alaska dropped south through western Canada. The cold front ahead of the trough crossed our area on the 27th and 28th. Gusty northwest winds followed the front.
In the valleys, rain soon changed to wet snow. Snow showers continued into the evening of the 28th, but they added little to the melting snow already on the ground.
On the 30 th , an upper level trough moving down the coast brought additional light snow.
