JACKSON, Wyo. – Rainfall from thunderstorms is often localized in nature, but we have seen substantial differences across the Teton Range so far in July. Jackson Hole Mountain Resort has received 2.0 to 2.5 inches of rain since July 1, while Driggs and Targhee have received less than a half-inch of rain over this same period.
Recent Weather and July Rainfall Variations
The weather pattern in July has been somewhat more active following a very dry June throughout the Greater Teton-Yellowstone region. But whether or not you have seen some good downpours this month depends on where you’re located.
The Southern Tetons and Jackson Hole Valley have consistently seen the stronger thunderstorms and the heaviest downpours this month, with lighter rainfall over the northern valley, and on the west side in Teton Valley and Targhee.
The town of Jackson has received 1.21 inches of rain in July and saw several heavy downpours over the previous week. That might not sound like a ton of rain, but July is the driest month of the year on average, with a monthly average of only 0.79 inches (data from 2010-2024).
Also, we only received 0.37 inches of rain in town during the entire month of June. So while this recent rainfall won’t come close to busting our drought, especially with high evaporation rates mid-summer, it’s been nice to receive some moisture after a bone-dry June.
Jackson Hole Mountain Resort has received the heaviest recorded rainfall amounts in the area during July, with rain gauges at the resort picking up between 2.0 and 2.5 inches so far this month.
To the south, Alpine has also received a solid 1.60 inches of rain so far this month.
Other areas have been much drier this month, however.
In the northern valley, rainfall totals around Jackson Lake and Moran have ranged from 0.6 to 0.8 inches. Rainfall amounts in Yellowstone have also been relatively modest.
In Teton Valley, rainfall amounts have generally been less than a half-inch, including 0.49 inches in Driggs and 0.41 inches in Alta.
Luck of the draw with summer thunderstorms accounts for some of these rainfall differences. Especially since we have had relatively few thunderstorm days, but with more of these storms producing locally heavy downpours (in other words, low consistency).
However, there are a couple of other possible explanations.
For one, when we have seen monsoonal moisture intrusions into our area from the south this month, the Jackson Hole Valley and Southern Tetons have been just on the northern and eastern edges of the more impressive moisture.
Another possible role is wind direction aloft coupled with terrain convergence around Teton Pass.
When we see monsoon moisture surges with more evenly distributed rainfall amounts from thunderstorms, winds aloft are often from the southwest or south/southwest.
While we have seen low-level moisture intrusions from the due south at times this month, upper level winds have typically been out of the due west, with storms traveling in a west to east or slightly west/southwest to east/northeast direction.
As storms have tracked over, or developed over, the Tetons with westerly winds aloft, the local terrain convergence where the Tetons meet the Snake River and Big Hole Ranges may be causing lower-level winds to converge around Victor and funnel up and over Teton Pass and the Southern Tetons, creating an orographic lifting effect that strengthens thunderstorms.
We have consistently seen stronger thunderstorms develop over Teton Pass and the Southern Tetons, before tracking through the lower valley, bringing heavy downpours to Teton Village, Wilson, and Jackson.
Keep in mind, this doesn’t always happen in the summer; it’s just been the case recently. Rainfall averages from Jackson to Moran to Driggs are fairly close to one another during the summer months, with Moran seeing slightly more on average.
Thunderstorm rainfall aside, temperatures have been fairly close to normal so far this July. Over the past week, highs have been in the 80s each day, while low temperatures have been milder due to increased winds from disturbances passing north of our area.
Upcoming Weather Pattern
If the discussion about recent rainfall during our driest month of the year (on average) seemed long-winded, that’s because the weather pattern over the next seven days is very boring!
We will see much drier conditions between now and July 29 as the monsoon over the Southwest is taking a break. A stubborn trough of low pressure has been located over California, leading to unseasonably cool temperatures there, while dry air at the base of the trough is scouring out monsoon moisture over the Southern Rockies for the time being.
Meanwhile, a series of Pacific disturbances will continue to track just a bit too far north of our area. As a result, we will continue to see dry weather, though a stray afternoon thunderstorm couldn’t entirely be ruled out on any given day.
Here is the 7-day precipitation forecast from the European Ensemble Model:
In terms of temperatures, highs will reach the mid 80s in Jackson each day from Thurday to Sunday, before heating up into the upper 80s to near 90 on Monday and Tuesday. The average high for the last week of July in Jackson is 84ºF for perspective.
Looking further out, there are some signs that we could see monsoon moisture sneak into our area around the end of July and beginning of August (mid to late next week), which would result in higher probabilities of thunderstorms.
Alan Smith, Meteorologist
