JACKSON, Wyo. – September 2022 will go down as one of the warmest Septembers on record in Teton County, thanks in part to a record-setting heatwave that occurred early in the month. However, rainfall was close to average in September, continuing what has been a fairly wet summer season.
September 2022 Review
September was much warmer than normal across Teton County and Northwest Wyoming, and across the Western U.S. as a whole. Although it will take a few more days for “official” stats to be released by the National Weather Service and other climate sources, this will almost certainly end up in the top five warmest Septembers on record in Teton County.
In the Town of Jackson, using weather data from the “official” NWS weather station, this month is in fifth place for the warmest Septembers on record. However, this station has exhibited an obvious under-reporting bias since about 2010 as evidenced by temperatures at surrounding stations.
If we look at temperature data from the Hydrometeorological Automated Data System (HADS) weather station in Jackson and compared it to historical data, this September would be the warmest on record in town, beating the old record set in 1998 by 0.3º F.
Elsewhere in Teton County, this September will also go down as the warmest on record in Alta and the sixth warmest on record in Moran. Technically, it will also go down as the warmest on record in Moose, but opposite of the Jackson station, the Moose weather station has exhibited a warm temperature bias since about 2010, so this should be taken with a grain of salt.
At the HADS weather station in Jackson, the average high temperature in September 2022 was 77.2ºF and the average low was 36.1ºF. These values are 4.8ºF warmer than normal.
The warmest temperature of the month was 92ºF, which occurred on September 6, and the coldest temperature of the month was 28ºF, which occurred on September 10 and 11.
Amazingly, the high temperature topped 90 degrees on five consecutive days in early September, which is extremely rare for so late in the year. Prior to September, Jackson had only hit 90ºF on two occasions this summer (once each in July and August), but the September heat pushed us up to seven days of 90ºF temperatures.
September started out very dry during the heatwave early in the month. However, the second half of September was much wetter as several low pressure systems impacted the area. These systems typically pulled in subtropical moisture from the remnants of tropical activity in the Eastern Pacific.
As a result, these systems were relatively mild in nature and snow levels stayed high throughout the month, with snow generally confined to the tops of the higher peaks and only occasionally falling down to 10,000 to 11,000 feet.
There were also several days in which thunderstorms occurred across Teton County, including September 29 when strong thunderstorms produced accumulating pea-sized hail in the Town of Jackson.
Jackson ended up receiving 1.52 inches of rain during the month of September (as of 9 a.m. on September 30), which is just barely below the long-term average of 1.60 inches. Across Teton County as a whole, precipitation in September was right around average.
The wettest 24-hour period occurred on September 21-22 when 0.54 inches of rain was recorded.
Despite the unseasonable warmth, frequent rainfall over the second half of the month prevented the drought situation from worsening, and the drought situation has remained unchanged across Teton County since the end of August.
Thankfully, abundant rainfall this summer kept our fire season quiet, and there were only a handful of days this summer when any smoke was present from distant fires.
Monthly Temperatures for Jackson (Water Year to Date Since October):
| Month | Avg High | Avg Low | Departure | Highest | Lowest |
| October | 56.5 | 29.0 | + 1.7 | 73 | 18 |
| November | 46.3 | 24.0 | + 7.4 | 59 | 6 |
| December | 35.3 | 21.0 | + 10.2 | 58 | -6 |
| January | 22.7 | -3.3 | – 7.0 | 42 | -19 |
| February | 29.9 | 3.0 | – 4.8 | 46 | -16 |
| March | 45.3 | 18.3 | + 0.8 | 66 | -15 |
| April | 46.0 | 24.1 | – 4.6 | 64 | 1 |
| May | 57.2 | 33.0 | – 2.6 | 79 | 18 |
| June | 71.2 | 38.6 | – 0.5 | 86 | 29 |
| July | 85.8 | 42.3 | + 2.2 | 93 | 35 |
| August | 82.7 | 46.5 | + 4.3 | 92 | 37 |
| September | 77.2 | 36.1 | + 4.8 | 92 | 28 |
| Water YTD | ? | ? | + 1.0 | ? | ? |
Monthly Precipitation for Jackson (Water Year to Date Since October):
| Month | Precipitation | Departure | Days of Precip | Snowfall | Departure |
| October | 1.71″ | + 0.30″ | 10 | 0.5″ | – 1.5″ |
| November | 1.35″ | – 0.36″ | 6 | 0.7″ | – 10.8″ |
| December | 1.83″ | + 0.19″ | 18 | 26.6″ | + 8.5″ |
| January | 1.23″ | – 0.05″ | 8 | 15.1″ | – 3.9″ |
| February | 0.29″ | – 0.89″ | 4 | 5.1″ | – 8.5″ |
| March | 0.66″ | – 0.60″ | 8 | 10.0″ | + 2.3″ |
| April | 1.95″ | + 0.65″ | 13 | 17.2″ | + 14.5″ |
| May | 2.19″ | – 0.01″ | 16 | 1.1″ | + 0.5″ |
| June | 1.58″ | + 0.08″ | 10 | 0.0″ | – |
| July | 0.06″ | – 1.06″ | 4 | 0.0″ | – |
| August | 3.65″ | + 2.42″ | 15 | 0.0″ | – |
| September | 1.52″ | – 0.08″ | 8 | 0.0″ | – |
| Water YTD | 18.02″ | + 0.58″ | 120 | 76.3″ | + 1.1″ |
October 2022 Outlook
We are well into the fall season now and the signs of the seasons changing are quite obvious in terms of shorter days, cooler temperatures and changing colors.
However, the overall pattern is favoring above-average temperatures in October, similar to recent months. So if you are looking to enjoy the last of summer’s activities before winter sets in, you may be in luck, at least through mid-month.
The first week or so of October is looking dry aside from some isolated showers during the weekend of October 1-2. Heading into the second week of October, the pattern may turn a bit more unsettled but significant precipitation and major cold snaps are unlikely through about mid-month.
During the second half of the month, it’s possible but uncertain that we could see stronger storm systems arrive eventually, and temperatures will likely trend cooler into late October as is typical with the changing seasons.
Overall, we can expect “equal chances” of above-average or below-average precipitation in October as there are no strong signals in either direction based on longer-range weather models.
In terms of historical averages for Jackson, the average high in October is 57.8ºF and the average low is 24.4ºF. Average precipitation is 1.41 inches and average snowfall is 2.0 inches with the first valley snow of the season typically occurring at some point during October.
Across the higher terrain, the Rendezvous Bowl Plot at Jackson Hole Mountain Resort (elevation 9,580 feet) averages 31 inches of snow in October and the Mid-Mountain Plot (elevation 8,180 feet) averages 19 inches of snow. By the end of October, the average snow depth (i.e. the amount of snow on the ground) at the Rendezvous Bowl Plot is 13 inches.
Bottom line, winter typically starts to set in across the higher elevations at some point in October, but the extent to which this happens varies significantly from year to year.
Also, one important thing to note is that October snowfall has absolutely no correlation to what the winter ahead will look like in terms of snowfall.
Alan Smith, Meteorologist
