Fall 2022 in Review

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.

Summer 2022 Season in Review

Temperatures were above or much above normal across most of the region. Precipitation was below or much below normal across Baker County Oregon and most of southwest Idaho. Only Harney and Malheur Counties, the lower Treasure Valley, and the southwest corner of Owyhee County were wetter than normal due to Pacific storms during the first half of June and monsoon thunderstorms in Harney, Baker, and southwest Owyhee Counties in August. 


June 2022 precipitationJune 2022 temperature

The first half of the month was dominated by westerly winds across the North Pacific which brought changeable weather to the northwestern U.S. Weather systems carried inland nearly daily showers from the 4th through the 8th.

On the 5th and 6th an upper level trough weakened as it moved inland, but it retained enough moisture and energy to generate strong thunderstorms across much of southwest Idaho. Hail up to 1.25 inches was reported at a number of locations.  Rainfalls  up to 1.25 inches were also measured. 

On the 10th warm air spreading north from the Great Basin raised temperatures above normal.

On the 12th a deep upper level trough, which had tapped abundant subtropical moisture, pushed inland. The cold front in advance of the trough was followed by a second front as the trough approached. The fronts triggered thunderstorms and heavy showers which dumped over an inch of rain at several locations. In Harney County north of Andrews a Mesonet station at Little McCoy Creek measured 2.23 inches. A Mesonet stations near Featherville in Elmore County measured nearly 3 inches. Local flooding was common around the region.  Wind gusts from 40 mph to around 50 mph were observed at several locations. 

The trough lingered through the 15th, keeping temperatures around 15 degrees below normal. Twin Falls recorded a record low of 37 on the 14th. On the 15th a record low of 26 was set at Burns.

Temperatures quickly rebounded on the 16th under southwest flow aloft ahead of the next trough. 

The cold front ahead of the trough moved into western Idaho late on the 16th. It stalled west of the Magic Valley, and Twin Falls recorded a record high of 94 on the 17th. Behind the front that same day highs were 10-15 degrees cooler.  The front finally exited east of our area late on the 17th, and the trough following the front kept temperatures 5-10 degrees below normal through the 20th.

By the 21st westerly flow aloft along the Canadian border had carried the trough east, allowing temperatures to recover to near normal.

On the 23rd a trough from the Gulf of Alaska had drifted south to southern B.C. and the Idaho panhandle. The cold front crossed the Boise area that afternoon, resulting in below-normal temperatures on the 24th and 25th. A record low of 41 was set at Twin Falls on the 25th.  

The trough rapidly exited eastward across southern Canada , allowing a very warm high amplitude ridge to build over the Intermountain Region, and the first really hot weather of the summer ensued. Highs from the mid 90s to a few degrees over 100 were common at lower elevations from the 26th through the 28th

A weak upper level trough moved over the area on the 29th, lowering  temperatures to near normal through the 30th.


July 2022 precipitation July 2022 temperature

On the 1st and 2nd a weak upper-level ridge and southwest flow aloft supported highs 5-10 degrees above normal.

On the 3rd an upper-level trough, which had been centered over Vancouver Island, began to edge inland. Cooler Pacific air associated with the trough lowered temperatures to near normal on the 3rd and below normal on the 4th.  Following the cold front on the 3rd, a wind gust of 67 mph at the Boise Airport knocked out power to the NIFC (National Interagency Fire Center).

Blocked by the ridge, the trough retreated back offshore on the 5th, allowing highs to rebound from the 5th through the 9th.

The trough moved back inland on the 9th, weakening as it encountered the strengthening ridge. The trough retained enough energy to spark thunderstorms. One storm produced three-quarter inch hail at Council. 

The ridge continued to strengthen and expand, and by the 12th it covered all of the western and south-central contiguous states.  Highs reached or exceeded 100 at lower elevations each day from the 12th through the 17th. 

A downburst from a thunderstorm at Burns on the 12th generated a wind gust of 67 mph. 

Meanwhile, another trough had migrated from the Aleutians across the Gulf of Alaska before crossing Washington and northern Idaho on the 18th. Cool air filtering south prevented temperatures from rising above 90 at most locations.

The trough continued on its eastward trek, allowing the ridge to expand northward again. Highs reached or surpassed 100 on the 20th in the lower valleys. 

Highs were around 5 degrees cooler from the 22nd through the 25th under the influence of a weak trough.

A new ridge developed off the coast and began to work its way inland on the 26th, resulting in another series of 100+ highs from the 26th through the 31st. 

Date       Location         Record high
7/17       Burns            100
           Twin Falls       100 tied record set in 2010
7/25       Burns             98 tied record set in 2021
7/26       Burns            102
7/27       Burns            101 tied record set in 1939
           Ontario          107 tied record set in 1964
7/28       Burns            103
           Ontario          109 
7/29       Boise            104 tied record set in 1934 
           Burns            103
           McCall            95 tied record set in 1994
           Ontario          111 national high!
7/30       Burns            103 tied record set in 2003
           McCall            96
           Baker            101 tied record set in 2003
7/31       Burns            104
           Ontario          102


On the 31st at Baker a thunderstorm downburst produced a gust of 62 mph. 


August 2022 precipitation August 2022 temperatures

A persistent upper level high pressure ridge was responsible for the record-setting heat.  On the 2nd as a Pacific cold front trailing south from Canada lowered highs by 10-15 degrees.  Temperatures rebounded on the 3rd and 4th ahead of the next Pacific cold front. That front passed on the 5th and lowered highs a few degrees on the 5th and 6th.

Warmer air returned on the 7th, and on the 8th highs exceeded 100 in the lower valleys.

On the 9th the ridge was centered over Wyoming and Colorado. Southerly flow between the ridge and an upper level low pressure center off the northern California coast began to pull monsoon moisture north over our area, resulting in scattered  thunderstorms from the 10th through the 12th

On the 10th there were reports of thunderstorm outflow gusts to around 60 mph in Malheur and Owyhee Counties. Heavy rain on the slopes of the Owyhee Mountains caused Rabbit Creek near Murphy to flood, with water over roads in places. A trained spotter at Murphy measured .78 of an inch of rain in 40 minutes. A spotter four miles southwest of Murphy measured 1.2 inches. 

On the 11th hail .5 to 1.5 inches in diameter fell at several locations in Canyon, Payette, and Owyhee Counties. On the 12th a trained spotter reported 1.5 inch hail at Oxbow Dam in Baker County, and a spotter at Yellow Pine reported 1.75 inch hail. 

On the 13th the low pressure center finally moved inland over southwest Canada. This allowed the upper level flow to shift into the southwest, bringing much drier air. 

From the 14th through the 24th highs in the valleys ranged from mid 90s to just over 100.

Monsoon moisture returned late in the day on the 18th as a weak low pressure trough approached from northern California. No unusual rainfalls were reported from thunderstorms on the 19th, but reports on social media described trees and power lines knocked down two miles northwest of McCall. The strongest gust measured at McCall airport was 45 mph. 

The heat persisted through the 26th.

By the 27th the upper level ridge center had relocated westward between Alaska and Hawaii, so flow across the North Pacific was no longer blocked from entering the northwest U.S. On the 27th a dry cold front crossed our area, resulting in a very pleasant weekend with highs near normal on the 27th and 28th.

On the 29th the upper level ridge over the Intermountain Region was already rebuilding, and temperatures were on their way up again.   The 106 at Boise on the 31st was the warmest ever so late in the season. 


Date         Location                 Record high
8/1          Burns                    100 tied record set in 2015
             McCall                    94
             Ontario                  109
8/13         Twin Falls                96
8/17         Boise                    103
             Burns                    103
             McCall                    97
             Twin Falls                99
             Baker                     99 tied record set in 2020
8/29         Burns                     95 tied record set in 2017
8/31         Boise                    106
             Burns                    101
             McCall                    95
             Ontario                  102
             Mountain Home            104
             Jerome                    99 tied record set in 1916
             Twin Falls               101
             Baker                    102             

Spring 2022 Season in Review

For the three-month period, temperatures were mainly below normal. Precipitation was above normal in Baker County Oregon and near to below normal elsewhere.


March precipitation anomalyMarch temperature anomaly

March was unusually dry. Much of our area received less than half normal precipitation.  Temperatures averaged near normal in the valleys, but above normal at higher elevations.

The month began with an upper level high pressure ridge over the region, resulting in above normal temperatures for the first three days of the month.

A cooling trend commenced when the ridge exited to the east on the 3rd and a ridge off the coast amplified northward into Alaska. This pattern brought cold dry air under northerly flow aloft.

By the 8th Arctic air had pushed south of the Canadian border into Montana, northern Idaho, and Washington. the Arctic front arrived in southern Idaho early on the morning of the 9th, leaving only light snowfalls. By that night the front was on its way south across Utah and Nevada.  Northwest winds which had gusted over 25 mph died down and skies cleared, allowing temperatures to dip into the teens and single digits by sunrise on the 10th. McCall’s low of minus 4 was not a record, but the lows of 14 at Boise and 9 at Twin Falls where previous records were 15 in 1948 at Boise and17 in 2006 at Twin Falls.

Temperatures quickly recovered on the 11th as a high pressure ridge moved inland, bringing warmer Pacific air. A weak upper level low pressure trough followed the ridge on the 13th.

On the 15th a stronger moister trough arrived from the Pacific. Precipitation was mainly less than two-tenths of an inch, but .41 inch was measured at McCall and .34 inch at Boise.

Westerly flow aloft continued to support near normal temperatures through the 18th. On the 19th the next trough brought light precipitation and cooler air.

The 20th was 10-15 degrees cooler behind the cold front, but the ridge which followed brought more spring like temperatures, with highs in the lower to mid 70s in the lower valleys from the 23rd through the 26th.  The ridge kept temperatures 5-10 degrees above normal through the 29th. The 75 at Burns on the 23rd tied the record set in 1940.

On the 30th another Pacific cold front was followed by gusty northwest winds, but little if any precipitation.  Temperatures cooled from normal on the 30th to below normal on the 31st as breezy northwest winds resumed.


April precipitation anomalyApril temperature anomaly

April was a cold, stormy, and windy month. All of our area as well as the entire northwestern U.S. averaged cooler than normal. Here are some of the record lows…


In contrast to the cold, Twin Falls set a record high of 80 on  April 8, eclipsing the old record for the date of 77 set in 2016.

Precipitation was generally above normal in southeast Oregon, southwest Owyhee County, and the central Idaho mountains. Elsewhere totals were near or slightly below normal.

At Boise, snowfall totaled 1.5 inches. That exceeds the April normal of 0.1 inch. The .3 inch on the 13th set a record for the date.

During the first 6 days of the month, strong westerly flow aloft carried weather systems from the Gulf of Alaska across the Pacific Northwest states.  On the 2nd the first of these systems brought no precipitation.

The next system on the 4th was stronger, but most locations received little or no precipitation. Exceptions were a quarter inch at Boise and half an inch at McCall. Strong winds followed the cold front, with gusts mainly in the 40-50 mph range. But there were several reports of gusts exceeding 60 mph.

An upper level high pressure ridge warmed temperatures to 10-20 degrees above normal on the 7th and 8th ahead of the next Pacific system.

On the 9th the ridge was replaced by an upper level trough, following another very windy cold front. Gusts of 40-50 mph were common, and there were a few reports of gusts exceeding 60 mph.

By the 10th the trough had expanded to cover much of central and western North America.  Unseasonably cold air kept temperatures in our area 10-15 degrees below normal.

Rain and snow fell daily from the 10th through the 14th as disturbances from the Gulf of Alaska dropped into the trough. Snowfall amounts were mostly under half an inch in the valleys, but 2.5 inches was measured near Twin Falls on the 11th, and 2.5 inches in Boise’s north end on the 12th. Also on the 12th 4.5 inches fell north of Donnelly. On the 14th 5.9 inches blanketed the ground near New Meadows.


More gusty northwest winds, mainly under 50 mph, followed a cold front on the 16th. A weak upper level ridge built over the region on the 17th, and on the 18th temperatures had warmed to around 10 degrees above normal. Cooler unsettled weather resumed on the 19th as an upper level trough off the coast sent impulses across our area.

The trough moved inland on the 22nd with another round of 40-50 mph winds. But most of its energy concentrated over southern California and the four-corners states, so most of our area was denied precipitation.  The high pressure ridge following the trough gave us the last warm weather of the month on the 25th ahead of another Pacific cold front.

The unsettled pattern redeveloped on the 26th as an upper level trough in  the Gulf of Alaska sent a series of disturbances inland across the Northwest. The first two systems dropped scarcely more than traces of precipitation.

On the 28th a cold front formed over Nevada and southwest Idaho, resulting in another episode of 40-50 mph winds.

On the 30th, showers and thunderstorms associated with an upper level trough brought generally light precipitation.


May precipitation anomaliesMay temperture anomaly

Unrelenting unseasonably cold and unsettled weather continued through much of May, but the latter half of the month brought long-awaited but brief hints of summer.

Precipitation was above or much above normal across most of our area.

The month began under an upper level low pressure trough which produced only light precipitation. A second stronger trough originating in the Gulf of Alaska brought more copious precipitation in the form of rain and snow, including .70 inch at Boise, .58 inch at McCall, .38 inch at Jerome, and .28 inch at Baker.

Here are a few snowfall reports on the 3rd…

9 inches 11 NE Garden City (Boise County) and 20 SSW of Silver City (Owyhee County)

7 inches 5 SW Donnelly (Valley County) and 15 W of Cambridge (Washington County)

6 inches 6 WSW Atlanta (Elmore County), 9 ESE Pioneerville (Boise County), 9 W Featherville (Elmore County), 16 E Rogerson (Twin Falls County), and 8 SE Three Creek (Twin Falls County)

5 inches 20 NNE McCall (Valley County)

4 inches 9 NNW Halfway (Baker County)

Precipitation started again on the evening of the 6th following a cold front which preceded a deepening trough from the Gulf of Alaska. Northwest winds in the 40-50 mph range were reported at many locations. Gusts of 69 mph were measured near Wagontire in Harney County and 62 mph near Kuna in Ada County.

As the trough took up residence over the Western Region on the 7th, it cooled highs by around 15 degrees and generated more rain and snow. McCall received .55 inch of precipitation, but amounts were generally light elsewhere.

A trough from the Bering Sea arrived over the coast on the 8th with even colder air. Snow began that night, and by the morning of the 9th the ground was white at many locations.

Here are a few reports…

11 Inches in Avimor (north Boise)

8 inches 6 N Boise (Ada County)

7 inches at Boise (Ada County)(totals ranged from 2 to 7 inches around Boise, but only half an inch at the airport, and a lot of tree damage in north Boise) and Cascade (Valley County)


4 inches at Centerville (Boise County), 4ENE Boise (Ada County), and 2E Emmett (Gem County)

3 inches at Garden City (Ada County)

2 inches at Mountain Home (Elmore County)

Generally light precipitation fell on the 12th and 13th as yet another trough from the Gulf of Alaska pushed inland along the Canadian border. A high pressure ridge building northward prevented most of the weather from penetrating very far south.

Temperatures rose steadily under the ridge, reaching the 80s at several locations on the 15th. Highs included 88 at Ontario and Rome, 85 at Boise and Mountain Home, 83 at Burns, 82 at Jerome, and 81 at Twin Falls.

Temperatures cooled to near normal from the 16th through the 18th as the ridge departed to the east and our area came under westerly flow aloft.

A cold front which passed late on the 18th brought gusts of 40-50 mph at many locations. Gusts exceeded 60 mph in the Twin Falls area.

The 19th were as much as 20 degrees cooler than the previous day.  The trough hung around through the 22nd.

Temperatures stayed below normal but gradually moderated as a high pressure ridge began to build inland. By the 25th highs were in the 80s again at lower elevations. Highs on the 25th and 26th included 82 and 91 at Jerome, 88 and 89 at Rome, 88 and 86 at Ontario, 85 and 89 at Mountain Home, 82 and 88 at Boise, 80 and 88 at Twin Falls, 82 and 81 at Burns, and 79 and 84 at Baker.

On the 26th a Pacific cold front was followed by another round of gusty northwest winds gusting to 40-50 mph.

On the 27th the trough following the cold front ushered in a wet period. And on the 28th a deeper, wetter, and colder trough, which originated in eastern Siberia, moved inland over the Pacific Northwest states. Finally on the 30th, a trough from southeast Alaska reinforced the main trough. Temperatures that day averaged as much at 20 degrees below normal.

Here are Precipitation totals(inches) for the 26th through the 31st…

Baker 1.41
Boise .85
Burns .31
Jerome 1.07
McCall .76
Mountain Home .97
Ontario .53
Rome .30
Twin Falls 1.04

As the trough began to exit southward over the Great Basin on the 31st, weak high pressure and partly cloudy skies started a warming trend.

2022 Idaho Spring Flood and Water Resources Outlook

Spring Flood PotentialSEWApr622

The risk for spring flooding due to snowmelt is low across Idaho. Snowpack in the lower valleys has melted out and the remaining mid and high elevation snowpack is well below normal for this time of year with the exception of northern Idaho where snowpack percentages are near normal. Snowpack in most basins peaked early and is on pace to melt out several weeks earlier than normal. 

The primary factors in the development of spring flooding are the occurrence of persistent above normal temperatures, and rain on snow precipitation events. Even if mainstem rivers do not reach flood stage, smaller creeks and streams can still overflow their banks. Under the right scenario, spring flooding is possible even for areas that have low snowpack. 


Water Supply 

NWSFApr622ational Weather Service water supply forecasts for April through September 2022 call for near normal runoff volumes for northern Idaho watersheds. Meanwhile, forecasts vary considerably across central and southern Idaho and are generally well below normal. Forecasts for the Snake River Headwaters near the Wyoming border and the Bear River in far southeast Idaho are generally 50 to 70 percent of normal. Volume forecasts for the Lost River Basins and Salmon River Basin are 60 to 80 percent of normal while forecasts for the Wood River Basins are 35 to 55 percent of normal. Forecasts for the Middle Snake River and the    Boise, Payette, and Weiser Basins range from 50 to 75 percent of normal. Across south central and southwest Idaho near the Nevada border runoff volumes are only expected to be 40 to 45 percent of normal. 


Temperature and Precipitation

In October, southern Idaho and the Panhandle Region had average to well above average precipitation while the Clearwater and Salmon River Basins in central Idaho were below average.  November precipitation was average to above average across the north while southern Idaho received well below average precipitation. Autumn was relatively warm statewide, especially in November when temperatures were 3 to 6 degrees (F) above average. December moisture varied considerably across Idaho but the majority of the state received average or above average precipitation. December temperatures were on the cool side across northern Idaho and a little above average across southern Idaho. 


January precipitation was below average across most of the state while temperatures were near average across northern Idaho and below average across the south. Northern regions of Idaho were a mix of below average and above average precipitation in February while record dryness occurred across central and southern Idaho. February was a cold month with below average temperatures throughout the state.  March precipitation was below average with the exception of some of the Idaho Panhandle where precipitation was near average. March temperatures were average to below average across northern and eastern Idaho and a little above average elsewhere across the state.  The three month period from January through March, 2022 was one of the driest on record for many locations across central and southern Idaho. 


Mountain snowpack was well above normal across most of the state in early January. However, snowpack percentages trended down afterward and by the end of February had decreased by 50 to 60 percentage points across much of central and southern Idaho. As of April 6, mountain snowpack was well below normal with the exception of northern Idaho where snowpack percentages are near normal. April 6 snowpack percentages were the highest in the Spokane and Clearwater Basins at 99 and 91 percent of median, while the lowest was in the Owyhee Basin at only 48 percent of median. Idaho snowpack as a whole typically builds through March and peaks in early April.



April 1 reservoir storage in northern Idaho, far southeast Idaho, on the Henrys Fork arm of the Upper Snake, the Payette Basin, and on the main stem Snake River was generally around normal. Elsewhere across central and southern Idaho, reservoir system storage ranged from 39 to 88 percent of normal. Reservoirs on the Snake River above Heise were at a combined 57 percent of normal. Magic Reservoir in south central Idaho was only at 39 percent of normal while Owyhee Reservoir was only 63 percent of normal. Weather patterns and irrigation demand will drive reservoir operations over the next several months. Wet spring weather or extended periods of above normal temperatures resulting in rapid snowmelt and large reservoir inflows could result in significant fluctuations in reservoir discharge and downstream river levels.


Drought continues to plague much of Idaho. Very dry conditions across much of central and southern Idaho from January through March have led to intensification of drought in some areas. Temperature and precipitation patterns for the remainder of spring and this summer will determine whether or not drought conditions improve or deteriorate. The U.S. Seasonal Drought Outlook indicates that drought is likely to persist across central and southern Idaho at least through the end of June. 


Long Range Outlook

The outlook for April through June favors below normal temperatures across the Idaho Panhandle and above normal temperatures for most of southern Idaho, and equal chances of either below, above, or normal temperatures elsewhere. The precipitation outlook favors below normal precipitation across central and southern Idaho, and equal chances for either below, above, or normal precipitation across the Idaho Panhandle.


Online Resources

Water Supply Volume Forecasts…
National Weather Service-Northwest River Forecast Center www.nwrfc.noaa.gov/ws/

National Weather Service-Colorado Basin River Forecast Center

USDA-Natural Resources Conservation Service

Snowpack Information…
National Weather Service-Northwest River Forecast Center

National Weather Service-National Operational Hydrologic Remote Sensing Center

USDA-Natural Resources Conservation Service

Reservoir Storage…
Bureau of Reclamation Reservoir Storage

USDA-Natural Resources Conservation Service

Drought Information…
U.S. Drought Portal

Peak Flow Forecasts…
Northwest River Forecast Center

Colorado Basin River Forecast Center

Temperature and Precipitation Outlook…
Climate Prediction Center