JACKSON, Wyo. — This meteorological summer season, which covers the three-month period from June through August, was the second hottest on record for Teton County dating back to 1895. This is based on recorded data from local weather stations and extrapolated data based on terrain courtesy of the PRISM model.

Temperatures during the summer of 2021 were 3.9ºF above the long-term average, trailing only 2007 which holds the record for the hottest summer in Teton County when temperatures were 4.63ºF above average.

PRISM Model Information

PRISM (Parameter-elevation Regressions on Independent Slopes Model) is a set of monthly, annual and single-event gridded meteorological data for 4-kilometer gridded areas throughout the United States.

The model takes into account recorded temperature and precipitation data from weather stations and uses a weighted scheme to produce additional estimates that account for complex terrain, mountains, rain shadows, temperature inversions, slope aspect, coastal influences and other micro-scale factors.

As a result, this model produces estimates that cover the entirety of Teton County (not to mention the U.S.) account for local terrain variations every 4 km. This results in a more accurate portrayal of current and past weather and climate conditions in an area such as Teton County which sees a significant terrain influence on weather.

Learn more about PRISM

Summer 2021 Summary

This summer, especially June and July, will go down as one of the hottest on record in the Western United States. Check out the PRISM percentile/rankings map below, with the darkest red color showing areas that experienced their hottest summer on record.

It’s no coincidence that many of the largest wildfires this summer have occurred in areas that experienced their hottest summer on record, such as California and Oregon.

The Southern Plains and parts of Deep South are the only areas of the U.S. that experienced a cooler than average summer – but of course, “cooler than average” in this region during the summer simply means “slightly less miserable!”

The weather station in the Town of Jackson (station ID JKNW4) recorded nine days of 90+ degree high temperatures this summer – one in June, seven in July and one in August. The hottest temperature of the summer in Jackson was 93ºF on July 28.

Outside of town, the Jackson Hole Airport recorded five 90-degree days and the Moran weather station near Jackson Lake recorded one 90-degree day.

The graph below shows how this summer stacks up compared to previous summers, dating back to 1895. This was the hottest summer in 14 years, but the long-term trend toward warmer summers is clear.

Keep in mind that the average temperature is the mid-point between the high and low temperature, at 4-km grid-points throughout Teton County, so don’t be fooled by the seemingly “cool” readings in the 50’s considering that elevation and low temperatures are factored in.

Here is a closer look at the summer departure from average temperatures since 1990. Notice a few cooler years in there in the past, most notably 1993 which was the coolest summer on record in Teton County and locally known as “the year without a summer.”

Now let’s take a look at the top five hottest summers on record in Teton County, including this year.

Hottest Summers (June-August) on Record in Teton County

  1. 2007 – 4.63ºF above average
  2. 2021 – 3.90ºF above average
  3. 2006 – 3.03ºF above average
  4. 2003 – 3.02ºF above average
  5. 1961 – 3.01ºF above average

Despite the warmth, precipitation during the summer of 2021 ended up being only slightly below average in Teton County (about 20% below average for the three-month period). Precipitation was below average in June and July, but well above average in August.

June 2021 Summary

Summer got off to a very hot and dry start in Jackson Hole, almost from the get-go in early June. This was not our typical June when we often experience late-season cool and wet systems mixed in with warmer days.

In fact, this June ended up being the hottest on record for Teton County with temperatures running 6.92ºF above average. It was also the second driest June on record with a county average precipitation of 0.27 inches, trailing only June 1919 for the driest on record.

Hottest June’s in Teton County

  1. 2021 – 6.92ºF above average
  2. 1988 – 6.72ºF above average
  3. 2015 – 6.70ºF above average
  4. 1900 – 5.56ºF above average
  5. 1961 – 5.26ºF above average

July 2021 Summary

This was the second hottest July on record for Teton County, trailing only 2007 which still holds the record by a wide margin. Precipitation was below-average, but not nearly as much so compared to June. In fact, the arrival of monsoonal moisture late in the month helped to quell the fire danger locally.

Hottest July’s in Teton County

  1. 2007 – 7.28ºF above average
  2. 2021 – 5.24ºF above average
  3. 2003 – 5.18ºF above average
  4. 2006 – 5.10ºF above average
  5. 1936 – 3.96ºF above average

 

August 2021 Summary

While this summer will be remembered as one of the hottest and smokiest summers, August saved us from having a bad fire season. Monsoonal moisture early in the month resulted in locally heavy rains around the county, then a series of fall-like weather systems produced substantial widespread rains during the second half of the month.

August ended up being the second wettest in the last 50 years and temperatures actually ended up slightly cooler than average for the month. The first half of the month was quite warm, similar to previous weeks and months, but the second half of the month was much cooler.

For comparison sake, here are the top 5 hottest August’s in Teton County:

  1. 2003 – 4.05ºF above average
  2. 2020 – 3.72ºF above average
  3. 1971 – 3.71ºF above average
  4. 2012 – 3.37ºF above average
  5. 2013 – 3.18ºF above average

 

This was certainly a summer to remember in Jackson Hole, but fortunately, it appears likely we will escape fire season without any major wildfires, though the risk for smaller wildland fires and rapid-spreading brush fires remains present (especially late this week).

Now, we just need to hope our smoke issues will subside sooner rather than later, and that we can start to put a dent in the drought over the upcoming wet season.

Alan Smith, Meteorologist

Alan is a professional meteorologist who holds a degree from MSU Denver and writes weather forecasts for Buckrail. He has lived in Jackson full-time since 2015. He is currently a Meteorologist and Operations Manager for OpenSnow, which is a weather forecasting service for skiing and outdoor adventures. At OpenSnow, Alan writes forecasts for the Tetons, Pacific Northwest, British Columbia, and North America as a whole.