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September Weather in Grand Teton National Park Wyoming, United States

Daily high temperatures decrease by 12°F, from 73°F to 61°F, rarely falling below 47°F or exceeding 81°F.

Daily low temperatures decrease by 8°F, from 39°F to 31°F, rarely falling below 23°F or exceeding 48°F.

For reference, on July 27, 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.

Average High and Low Temperature in September in Grand Teton National Park

Average High and Low Temperature in September in Grand Teton National ParkSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303010°F10°F20°F20°F30°F30°F40°F40°F50°F50°F60°F60°F70°F70°F80°F80°F90°F90°FAugOctSep 173°FSep 173°F39°F39°FSep 3061°FSep 3061°F31°F31°FSep 1170°FSep 1170°F37°F37°FSep 2165°FSep 2165°F34°F34°FNowNow
The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on September. 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.

Average Hourly Temperature in September in Grand Teton National Park

Average Hourly Temperature in September in Grand Teton National ParkSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMAugOctNowNowfreezingvery coldcoldcoolcomfortablewarmfreezing
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The average hourly temperature, color coded into bands. The shaded overlays indicate night and civil twilight.
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The month of September in Grand Teton National Park experiences gradually increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 28% to 35%.

The clearest day of the month is September 4, with clear, mostly clear, or partly cloudy conditions 72% of the time.

For reference, on March 17, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 58%, while on July 27, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 78%.

Cloud Cover Categories in September in Grand Teton National Park

Cloud Cover Categories in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 172%Sep 172%Sep 3065%Sep 3065%Sep 1170%Sep 1170%Sep 2167%Sep 2167%NowNowclearmostly clearpartly cloudyovercastmostly cloudy
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds.

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 September is gradually increasing, starting the month at 17% and ending it at 19%.

For reference, the year's highest daily chance of a wet day is 32% on May 29, and its lowest chance is 14% on July 3.

Over the course of September in Grand Teton National Park, the chance of a day with only rain remains an essentially constant 17% throughout, the chance of a day with mixed snow and rain remains an essentially constant 1% throughout, and the chance of a day with only snow remains an essentially constant 0% throughout.

Probability of Precipitation in September in Grand Teton National Park

Probability of Precipitation in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%2%2%4%4%6%6%8%8%10%10%12%12%14%14%16%16%18%18%20%20%22%22%24%24%AugOctSep 117%Sep 117%Sep 3019%Sep 3019%Sep 1117%Sep 1117%Sep 2119%Sep 2119%NowNowsnowmixedrain
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

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

The average sliding 31-day rainfall during September in Grand Teton National Park is essentially constant, remaining about 1.0 inches throughout, and rarely exceeding 2.4 inches or falling below 0.1 inches.

The highest average 31-day accumulation is 1.1 inches on September 30.

Average Monthly Rainfall in September in Grand Teton National Park

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average snowfall.

Over the course of September in Grand Teton National Park, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 26 minutes, implying an average daily decrease of 2 minutes, 58 seconds, and weekly decrease of 20 minutes, 43 seconds.

The shortest day of the month is September 30, with 11 hours, 44 minutes of daylight and the longest day is September 1, with 13 hours, 10 minutes of daylight.

Hours of Daylight and Twilight in September in Grand Teton National Park

Hours of Daylight and Twilight in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hrAugOctSep 2212 hr, 11 minSep 2212 hr, 11 minnightnightdaydaySep 113 hr, 10 minSep 113 hr, 10 minNowNow
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Grand Teton National Park is 6:46 AM on September 1 and the latest sunrise is 33 minutes later at 7:19 AM on September 30.

The latest sunset is 7:57 PM on September 1 and the earliest sunset is 53 minutes earlier at 7:04 PM on September 30.

Daylight saving time is observed in Grand Teton National Park during 2024, but it neither starts nor ends during September, so the entire month is in daylight saving time.

For reference, on June 20, 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.

Sunrise & Sunset with Twilight in September in Grand Teton National Park

Sunrise & Sunset with Twilight in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930302 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMAugOct6:46 AM6:46 AMSep 17:57 PMSep 17:57 PM7:19 AM7:19 AMSep 307:04 PMSep 307:04 PM6:58 AM6:58 AMSep 117:39 PMSep 117:39 PMSolarMidnightSolarMidnightSolarNoonSunriseSunsetNowNow
The solar day over the course of September. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

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.

Solar Elevation and Azimuth in September in Grand Teton National Park

Solar Elevation and Azimuth in September in Grand Teton National ParkSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM2 AM2 AM4 AM4 AM6 AM6 AM8 AM8 AM10 AM10 AM12 PM12 PM2 PM2 PM4 PM4 PM6 PM6 PM8 PM8 PM10 PM10 PM12 AM12 AMAugOct001010202020303040405000010102020303030405060NowNow
northeastsouthwest
Solar elevation and azimuth over the course of September 2024. The black lines are lines of constant solar elevation (the angle of the sun above the horizon, in degrees). The background color fills indicate the azimuth (the compass bearing) of the sun. The lightly tinted areas at the boundaries of the cardinal compass points indicate the implied intermediate directions (northeast, southeast, southwest, and northwest).

The figure below presents a compact representation of key lunar data for September 2024. 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.

Moon Rise, Set & Phases in September in Grand Teton National Park

Moon Rise, Set & Phases in September in Grand Teton National ParkSep11223344556677889910101111121213131414151516161717181819192020212122222323242425252626272728282929303012 AM12 AM4 AM4 AM8 AM8 AM12 PM12 PM4 PM4 PM8 PM8 PM12 AM12 AMAugOctAug 45:14 AMAug 45:14 AMAug 1912:26 PMAug 1912:26 PMSep 27:56 PMSep 27:56 PMSep 178:35 PMSep 178:35 PMOct 212:50 PMOct 212:50 PMOct 175:27 AMOct 175:27 AM6:09 AM6:09 AM9:16 PM9:16 PM8:13 PM8:13 PM6:08 AM6:08 AM6:13 AM6:13 AM8:02 PM8:02 PM7:27 PM7:27 PM7:44 AM7:44 AM7:13 AM7:13 AM6:59 PM6:59 PM6:11 PM6:11 PM7:56 AM7:56 AM
The time in which the moon is above the horizon (light blue area), with new moons (dark gray lines) and full moons (blue lines) indicated. The shaded overlays indicate night and civil twilight.
Sep 2024IlluminationMoonriseMoonsetMoonriseMeridian PassingDistance
1
2%5:07 AMENE7:43 PMWNW-12:30 PMS249,284 mi
2
0%6:13 AMENE8:02 PMWNW-1:11 PMS250,656 mi
3
1%7:17 AME8:19 PMW-1:51 PMS251,665 mi
4
3%8:19 AME8:35 PMW-2:29 PMS252,264 mi
5
7%9:21 AME8:51 PMW-3:08 PMS252,389 mi
6
13%10:24 AMESE9:09 PMWSW-3:47 PMS251,966 mi
7
20%11:28 AMESE9:29 PMWSW-4:29 PMS250,919 mi
8
28%12:34 PMESE9:54 PMWSW-5:14 PMS249,195 mi
9
38%1:41 PMSE10:25 PMSW-6:03 PMS246,775 mi
10
48%2:48 PMSE11:05 PMSW-6:57 PMS243,696 mi
11
50%3:51 PMSE11:57 PMSW-7:54 PMS240,069 mi
12
69%4:47 PMSE--8:54 PMS236,093 mi
13
79%-1:01 AMSW5:33 PMSE9:54 PMS232,049 mi
14
88%-2:16 AMSW6:09 PMESE10:53 PMS228,281 mi
15
95%-3:36 AMWSW6:39 PMESE11:49 PMS225,156 mi
16
97%-4:59 AMWSW7:04 PMESE--
17
100%-6:22 AMW7:27 PME12:42 AMS222,999 mi
18
100%-7:44 AMW7:49 PME1:33 AMS222,044 mi
19
98%-9:06 AMWNW8:12 PMENE2:24 AMS222,383 mi
20
92%-10:29 AMWNW8:38 PMENE3:15 AMS223,954 mi
21
85%-11:52 AMWNW9:09 PMENE4:09 AMS226,552 mi
22
75%-1:12 PMNW9:48 PMNE5:05 AMS229,876 mi
23
64%-2:26 PMNW10:37 PMNE6:04 AMS233,585 mi
24
50%-3:29 PMNW11:35 PMNE7:02 AMS237,356 mi
25
42%-4:18 PMNW-7:59 AMS240,924 mi
26
31%12:41 AMNE4:56 PMNW-8:53 AMS244,106 mi
27
22%1:50 AMENE5:26 PMWNW-9:43 AMS246,796 mi
28
15%2:58 AMENE5:49 PMWNW-10:29 AMS248,954 mi
29
8%4:04 AMENE6:09 PMWNW-11:11 AMS250,582 mi
30
4%5:09 AMENE6:26 PMW-11:51 AMS251,710 mi

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 September, remaining around 0% throughout.

Humidity Comfort Levels in September in Grand Teton National Park

Humidity Comfort Levels in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%0%10%10%20%20%30%30%40%40%50%50%60%60%70%70%80%80%90%90%100%100%AugOctSep 160%Sep 160%Sep 10%Sep 10%Sep 300%Sep 300%NowNowdrydry
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The percentage of time spent at various humidity comfort levels, categorized by dew point.

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 September, remaining within 0.1 miles per hour of 4.8 miles per hour throughout.

For reference, on March 29, the windiest day of the year, the daily average wind speed is 5.4 miles per hour, while on August 4, the calmest day of the year, the daily average wind speed is 4.7 miles per hour.

The highest daily average wind speed during September is 4.9 miles per hour on September 5.

Average Wind Speed in September in Grand Teton National Park

Average Wind Speed in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 mph0 mph1 mph1 mph2 mph2 mph3 mph3 mph4 mph4 mph5 mph5 mph6 mph6 mph7 mph7 mphAugOctSep 54.9 mphSep 54.9 mphSep 304.8 mphSep 304.8 mphSep 164.8 mphSep 164.8 mphNowNow
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The hourly average wind direction in Grand Teton National Park throughout September is predominantly from the west, with a peak proportion of 48% on September 30.

Wind Direction in September in Grand Teton National Park

Wind Direction in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%20%80%40%60%60%40%80%20%100%0%AugOctNowNowwestsoutheastnorth
northeastsouthwest
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions, excluding hours in which the mean wind speed is less than 1.0 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

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 18 to around August 29, rarely starting before May 24 or after July 11, and rarely ending before August 6 or after September 17.

The month of September 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 43% to 1% over the course of the month.

Time Spent in Various Temperature Bands and the Growing Season in September in Grand Teton National Park

Time Spent in Various Temperature Bands and the Growing Season in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%AugOctSep 143%Sep 143%Sep 301%Sep 301%Sep 1120%Sep 1120%Sep 216%Sep 216%50%Aug 2950%Aug 2990%Aug 690%Aug 6NowNowfreezingvery coldcoldcoolcomfortablewarmfrigid
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The percentage of time spent in various temperature bands. The black line is the percentage chance that a given day is within the growing 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 gradually increasing during September, increasing by 162°F, from 1,077°F to 1,239°F, over the course of the month.

Growing Degree Days in September in Grand Teton National Park

Growing Degree Days in September in Grand Teton National ParkSep112233445566778899101011111212131314141515161617171818191920202121222223232424252526262727282829293030900°F900°F1,000°F1,000°F1,100°F1,100°F1,200°F1,200°F1,300°F1,300°F1,400°F1,400°F1,500°F1,500°FAugOctSep 11,077°FSep 11,077°FSep 301,239°FSep 301,239°FSep 111,150°FSep 111,150°FNowNow
The average growing degree days accumulated over the course of September, with 25th to 75th and 10th to 90th percentile bands.

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 rapidly decreasing during September, falling by 1.5 kWh, from 6.1 kWh to 4.6 kWh, over the course of the month.

Average Daily Incident Shortwave Solar Energy in September in Grand Teton National Park

Average Daily Incident Shortwave Solar Energy in September in Grand Teton National ParkSep1122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930300 kWh0 kWh1 kWh1 kWh2 kWh2 kWh3 kWh3 kWh4 kWh4 kWh5 kWh5 kWh6 kWh6 kWh7 kWh7 kWh8 kWh8 kWh9 kWh9 kWhAugOctSep 16.1 kWhSep 16.1 kWhSep 304.6 kWhSep 304.6 kWhSep 115.7 kWhSep 115.7 kWhNowNow
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

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%).

This report illustrates the typical weather in Grand Teton National Park, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

The details of the data sources used for this report can be found on the Jackson Hole Airport page.

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The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

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