Fall Weather in Grand Teton National Park Wyoming, United States

Daily high temperatures decrease by 43°F, from 74°F to 30°F, rarely falling below 19°F or exceeding 82°F.

Daily low temperatures decrease by 27°F, from 39°F to 12°F, rarely falling below -5°F or exceeding 48°F.

For reference, on July 28, the hottest day of the year, temperatures in Grand Teton National Park typically range from 44°F to 80°F, while on January 27, the coldest day of the year, they range from 6°F to 25°F.

The figure below shows you a compact characterization of the hourly average fall temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

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The fall in Grand Teton National Park experiences very rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 28% to 56%.

The clearest day of the fall is September 1, with clear, mostly clear, or partly cloudy conditions 72% of the time.

For reference, on March 18, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 58%, while on July 28, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 78%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Grand Teton National Park, the chance of a wet day over the course of the fall is very rapidly increasing, starting the season at 17% and ending it at 27%.

For reference, the year's highest daily chance of a wet day is 32% on May 30, and its lowest chance is 14% on July 4.

Over the course of the fall in Grand Teton National Park, the chance of a day with only rain decreases from 16% to 5%, the chance of a day with mixed snow and rain increases from 0% to 7%, and the chance of a day with only snow increases from 0% to 14%.

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the fall in Grand Teton National Park is gradually decreasing, starting the season at 0.9 inches, when it rarely exceeds 1.8 inches or falls below 0.2 inches, and ending the season at 0.7 inches, when it rarely exceeds 1.7 inches or falls below 0.1 inches.

The highest average 31-day accumulation is 1.1 inches on October 1.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during the fall in Grand Teton National Park is very rapidly increasing, starting the season at 0.0 inches, when it rarely exceeds 0.0 inches or falls below -0.0 inches, and ending the season at 10.9 inches, when it rarely exceeds 20.5 inches or falls below 2.9 inches.

Over the course of the fall in Grand Teton National Park, the length of the day is very rapidly decreasing. From the start to the end of the season, the length of the day decreases by 4 hours, 0 minutes, implying an average daily decrease of 2 minutes, 40 seconds, and weekly decrease of 18 minutes, 41 seconds.

The shortest day of the fall is November 30, with 9 hours, 11 minutes of daylight and the longest day is September 1, with 13 hours, 11 minutes of daylight.

The earliest sunrise of the fall in Grand Teton National Park is 6:46 AM on September 1 and the latest sunrise is 1 hour, 13 minutes later at 7:59 AM on November 1.

The latest sunset is 7:57 PM on September 1 and the earliest sunset is 3 hours, 11 minutes earlier at 4:46 PM on November 30.

Daylight saving time (DST) ends at 1:00 AM on November 2, 2025, shifting sunrise and sunset to be an hour earlier.

For reference, on June 21, the longest day of the year, the Sun rises at 5:40 AM and sets 15 hours, 28 minutes later, at 9:08 PM, while on December 21, the shortest day of the year, it rises at 7:53 AM and sets 8 hours, 55 minutes later, at 4:48 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for the fall of 2025. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Grand Teton National Park is essentially constant during the fall, remaining around 0% throughout.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Grand Teton National Park is essentially constant during the fall, remaining within 0.2 miles per hour of 4.9 miles per hour throughout.

For reference, on March 30, the windiest day of the year, the daily average wind speed is 5.4 miles per hour, while on August 5, the calmest day of the year, the daily average wind speed is 4.7 miles per hour.

The hourly average wind direction in Grand Teton National Park throughout the fall is predominantly from the west, with a peak proportion of 49% on October 26.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Grand Teton National Park typically lasts for 2.4 months (72 days), from around June 19 to around August 30, rarely starting before May 25 or after July 12, and rarely ending before August 7 or after September 18.

The fall in Grand Teton National Park is more likely than not fully outside of the growing season, with the chance that a given day is in the growing season rapidly decreasing from 45% to 0% over the course of the season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Grand Teton National Park are increasing during the fall, increasing by 215°F, from 1,077°F to 1,292°F, over the course of the season.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Grand Teton National Park is very rapidly decreasing during the fall, falling by 4.2 kWh, from 6.2 kWh to 2.0 kWh, over the course of the season.

For the purposes of this report, the geographical coordinates of Grand Teton National Park are 43.790 deg latitude, -110.682 deg longitude, and 6,424 ft elevation.

The topography within 2 miles of Grand Teton National Park contains only modest variations in elevation, with a maximum elevation change of 282 feet and an average elevation above sea level of 6,923 feet. Within 10 miles contains only modest variations in elevation (7,192 feet). Within 50 miles also contains extreme variations in elevation (8,694 feet).

The area within 2 miles of Grand Teton National Park is covered by shrubs (54%) and trees (40%), within 10 miles by shrubs (45%) and trees (27%), and within 50 miles by trees (44%) and shrubs (36%).