JACKSON, Wyo. – July was drier than average across Teton County and the town of Jackson recorded more 90-degree days than usual, though temperatures for the month as a whole ended up right around average. Wildfire smoke has also been a nuisance since mid-July.
July 2024 Recap
For the second month in a row, rainfall was well below average across Teton County. While summers are typically drier and sunnier than other seasons in our area, this summer has been much drier than average so far.
The town of Jackson only received 0.29 inches of rain in July, which is well below the July average of 0.82 inches.
Also, Jackson has only received a total of 0.82 inches of rain since June 1, making this the driest June-July period in town in over 20 years (since 2003). By comparison, last summer Jackson received 3.19 inches of rain between June 1 and July 31.
Other locations in Teton County did not fare much better, even with the hit-or-miss nature of thunderstorms. Rainfall amounts for most of the county ranged from 25 to 75% of average.
The Western U.S. as a whole was also drier than average, aside from isolated areas that saw heavy rain-producing thunderstorms.
July sure did “seem” like a hot month in Jackson, but believe it or not, temperatures ended up right around average for the month as a whole. The average high and low for July 2024 in Jackson were 83.2ºF and 42.7ºF respectively.
When averaging the high and low temperatures together, temperatures ended up 0.2ºF below normal in Jackson this month and 0.3ºF above normal at the Moran/Jackson Lake weather station. In other words, temperatures were right around long-term averages.
Areas to our west experienced the most extreme and consistent heat in July with temperatures running well above average. Not coincidentally, areas such as Oregon and Northern California that saw well above average heat, have also experienced numerous large wildfires.
Even though the month ended up near average as a whole in terms of temperature, there were some stretches of very hot weather by our standards.
The town of Jackson ended up with eight 90-degree days in July, which is the most 90-degree days in one month since July 2007. Jackson only averages four 90-degree days per year, and we doubled that in July alone.
If we had so many more 90-degree days than usual, then how did temperatures end up right at average in July?
As it turns out, we also had some extended stretches of below-average temperatures, mainly during the first week of the month and again during the final week of the month.
Also, overnight lows were a bit cooler than usual, partly due to drier-than-usual air masses which allowed for strong radiational cooling at night. There were nine mornings in which lows dipped into the 30s in Jackson in July, including two mornings early in the month when the low fell to 33ºF.
Another oddity is that average low temperatures were cooler in July than they were in June in Jackson. This is the first time this has happened since 1997.
Unfortunately, smoke became an ever-present visitor in Jackson starting as early as the second week of July, and air quality significantly deteriorated during the final days of the month.
Wildfires in Eastern Oregon were the main culprit for much of the month, and more recently, the nearly 400,000-acre Park Fire in Northern California has been a major contributor. Fortunately, we are now getting a break in the smoke as of this writing.
Current and Upcoming Weather Pattern
We are finally enjoying some better air quality as of Wednesday afternoon. A trough of low pressure moved across the area on Tuesday, along with a cold front, which helped to push the plume of smoke over our area further south.
Initially, the smoke did not clear quickly in Jackson on Wednesday morning. This is because a morning inversion kept the smoke “trapped” in the valley. The heavy smoke eventually dispersed in the hours after the inversion eroded.
Air quality is still “Moderate” as of this writing on Wednesday afternoon, so the smoke isn’t entirely gone, but conditions are significantly improved compared to prior days.
From Thursday through Saturday, a ridge of high pressure will build over the Western U.S. and southerly winds near the Park Fire in California should keep the worst of the smoke away from us for the time being, though light smoke will remain possible at times.
Temperatures will also heat up significantly during this time with highs in the upper 80s on Thursday and low 90s on Friday and Saturday.
On Sunday, monsoonal moisture will push into our area from the southwest and should settle into place for a longer period of time, unlike in recent weeks when we only saw fleeting and weaker moisture surges.
As a result, we will likely enter a pattern of daily to near-daily thunderstorm chances from Sunday on. Temperatures should also moderate a bit with highs in the upper 80s on Sunday and low to mid 80s by around the middle of next week.
There is also a chance that wildfire smoke could increase across our area again next week as winds near the California and Oregon fires gradually shift from southerly back to westerly. However, this is also dependent on fire behavior with ongoing fires along with the potential for new fires.
August Outlook
August is the second hottest month of the year in Jackson Hole behind July. Highs in the 80s are common during the first half of the month, but temperatures typically start to cool off during the second half of the month.
In the town of Jackson, the average high in August is 81ºF and the average low is 42ºF based on the previous 15 years.
Jackson typically hits 90 degrees at least once during the month of August. However, freezing low temperatures are also not uncommon late in the month. In fact, during the previous 15 years, the average first freeze date in Jackson is August 28.
The town of Jackson averages 1.48 inches of rain during August, which is quite a bit more than July. There are an average of 11 thunderstorm days in the Jackson Hole area during August, which is the most of any month and slightly above July’s average of 10 thunderstorm days.
The reason for the uptick in average rainfall in August is because the North American Monsoon (a seasonal circulation of subtropical moisture over the Southwest U.S.) typically strengthens during the first half of August, with stronger and more consistent northward moisture surges reaching our area.
August has been very wet in Jackson Hole in recent years, and interestingly enough, over the past 20 years, we have seen a trend toward drier Julys and wetter Augusts. During each of the previous three years, Jackson recorded at least three inches of rain during August.
Will the trend of wet Augusts continue in 2024?
Medium-range models are projecting more consistent moisture from the monsoon to reach our area starting on Sunday and perhaps continuing through mid-month. This will at least give us a chance to see more meaningful rainfall, though there is some uncertainty given the hit-or-miss nature of thunderstorms.
However, longer-range weather models as well as NOAA’s Climate Prediction Center are projecting below-average rainfall for the month as a whole, despite the potentially active start to the month.
Overall, confidence is low in terms of how August rainfall will play out, though we will likely see more than we did in July at least.
Temperatures are also projected to be hotter than average overall in Jackson, though medium-range models are hinting at the potential for a cooler period around mid-month.
August will be a crucial month, as another hot and dry month would lead to rising fire danger. But if the monsoon delivers on a consistent basis and brings us more frequent rainfall, that could help to temper fire danger. We’ll see what happens…
Alan Smith, Meteorologist
