West Yellowstone, MT weather in September
September in West Yellowstone: mild, with some rain. Highs 68°F, lows 37°F, about 7 days with rain. A great month for outdoor plans.
- Normal high
- 68°F
- Normal low
- 37°F
- Wet days
- 7
- 1.7 in total
- Muggy days
- 0
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 74°F | 60°F |
| Normal low | 40°F | 33°F |
| Chance of a wet day | 21% | 26% |
| Sunrise / sunset | 6:47 am / 8:01 pm | 7:21 am / 7:07 pm |
| Daylight | 13.3 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Mountain Time).
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F18 of 30
- Hot dayshigh 90°F or more0 of 30
- Muggy daysdaily mean dew point 65°F or more0 of 30
- Wet daysat least 0.01 in of rain or melted snow7 of 30
- Notable rainat least 0.10 in7 of 30
- Freezing nightslow 32°F or below7 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 1.7 in; a dry September brings about 0.8 in and a wet one about 2.5 in (25th and 75th percentiles). About 1 day brings half an inch or more. Snow is very rare.
How September varies from year to year
- Warmest September, 1991-20202009: average high 76°F
- Coolest September2000: average high 64°F
- Wettest September2017: 4.3 in
- Driest September2009: 0.2 in
- Highest reading91°F (September 5, 2020)
- Lowest reading17°F (September 24, 2000)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 78°F | 68°F | 51°F |
| Normal low | 43°F | 37°F | 28°F |
| Wet days | 6 | 7 | 10 |
| Comfortable days | 18 | 18 | 4 |
| Daylight | 14.0 h | 12.5 h | 11.0 h |
Highs change by -10°F from August and -17°F into October.
Nearby alternatives in September
- Warmer: Billings, MT148 mi · high 75°F · 7 wet days
How West Yellowstone ranks in September
- Normal high362nd warmest of 378 cities; 6th of 6 in Montana
- Wet days142nd driest of 378
- Comfortable days28th most of 342
What to pack for West Yellowstone in September
- A warm jacket – lows near 37°F, highs near 68°F
- Layers – afternoons near 68°F but nights near 37°F
Frost in September
The first fall frost typically comes around Sep 10; in 1 year in 10 it comes before Aug 25. All frost dates for West Yellowstone.
Heating and cooling
September has 377 heating degree days and 1 cooling degree days (base 65°F), 4% of the year's total heating and cooling demand.
Questions
How cold is West Yellowstone in September?
The normal high is 68°F and the normal low is 37°F. From 1991 to 2020 the coldest September reading was 17°F (most recently on September 24, 2000).
Does it rain a lot in West Yellowstone in September?
About 7 days in September have at least 0.01 in of precipitation, and the normal total is 1.7 in. The wettest September in 1991-2020 was in 2017 (4.3 in); the driest was in 2009 (0.2 in).
Does it snow in West Yellowstone in September?
Snow is very rare: the 1991-2020 normal for September rounds to 0.0 in.
Is September a good time to visit West Yellowstone?
September ranks 4th of 12 months on our comfort score for West Yellowstone (72 out of 100). It has about 18 comfortable days. The best months are June, July and August.
Where the numbers come from
- Temperature, snowfall, snow depth and frost dates: Hebgen Dam (USC00244038), 18 mi NW of the city center, 6,489 ft (178 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Rain: Whiskey Creek (USS0011E30S), 4.2 mi SSW of the city center, 6,800 ft (133 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Yellowstone (726664-94173), 35 mi ESE of the city center, 7,782 ft (1,115 ft higher than the city). Hourly observations, 1991-2020.
- Not available for this location: humidity and wind by hour and cloud cover (no station close enough or similar enough in elevation).