Big Sky Weather in September
Average highs run from 73°F on September 1 to 62°F on September 30, and lows from 36°F to 30°F. Normal precipitation for the month is 1.70 in over about 10 wet days.
September day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
September at a glance
- Average high
- 68°F
- Average low
- 33°F
- Precipitation
- 1.70 in
- Snowfall
- 0.1 in
- Record high
- 98°FSep 4, 2022
- Record low
- 10°FSep 29, 1985
- Chance of a freeze
- 100%
- Daylight
- 13 h 16 min to 11 h 44 min
- Cloud cover
- 52%
- Humidity
- 55%
- Dew point
- 33°F
- Wind
- 5.4 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| Sep 1 | 73°F | 36°F | 92°F 1967 | 22°F 1930 | 34% | 0% |
| Sep 2 | 73°F | 36°F | 94°F 2024 | 24°F 2006 | 34% | 0% |
| Sep 3 | 72°F | 36°F | 92°F 2007 | 28°F 2006 | 34% | 0% |
| Sep 4 | 72°F | 36°F | 98°F 2022 | 26°F 1929 | 34% | 0% |
| Sep 5 | 72°F | 36°F | 94°F 1967 | 27°F 2014 | 33% | 0% |
| Sep 6 | 72°F | 35°F | 96°F 2020 | 27°F 2014 | 33% | 0% |
| Sep 7 | 71°F | 35°F | 95°F 2022 | 21°F 1929 | 33% | 0% |
| Sep 8 | 71°F | 35°F | 97°F 2022 | 22°F 1929 | 33% | 0% |
| Sep 9 | 71°F | 35°F | 93°F 2021 | 22°F 2020 | 33% | 0% |
| Sep 10 | 70°F | 35°F | 89°F 1966 | 26°F 1921 | 33% | 0% |
| Sep 11 | 70°F | 35°F | 88°F 1981 | 22°F 1989 | 33% | 0% |
| Sep 12 | 70°F | 34°F | 90°F 1953 | 20°F 2014 | 33% | 0% |
| Sep 13 | 69°F | 34°F | 89°F 1948 | 22°F 1974 | 33% | 0% |
| Sep 14 | 69°F | 34°F | 88°F 1948 | 25°F 1961 | 33% | 1% |
| Sep 15 | 69°F | 34°F | 93°F 2000 | 22°F 1970 | 33% | 1% |
| Sep 16 | 68°F | 34°F | 90°F 2000 | 22°F 1936 | 33% | 1% |
| Sep 17 | 68°F | 33°F | 89°F 1981 | 20°F 1965 | 33% | 1% |
| Sep 18 | 68°F | 33°F | 88°F 1981 | 17°F 1965 | 32% | 1% |
| Sep 19 | 67°F | 33°F | 89°F 1922 | 18°F 1965 | 32% | 1% |
| Sep 20 | 67°F | 33°F | 89°F 1922 | 12°F 1983 | 32% | 1% |
| Sep 21 | 66°F | 32°F | 89°F 1922 | 21°F 1995 | 32% | 1% |
| Sep 22 | 66°F | 32°F | 86°F 1966 | 19°F 1971 | 32% | 1% |
| Sep 23 | 65°F | 32°F | 89°F 1987 | 16°F 1934 | 31% | 1% |
| Sep 24 | 65°F | 32°F | 89°F 2001 | 12°F 1926 | 31% | 2% |
| Sep 25 | 64°F | 31°F | 88°F 1994 | 12°F 1926 | 31% | 2% |
| Sep 26 | 64°F | 31°F | 88°F 2015 | 15°F 1926 | 31% | 2% |
| Sep 27 | 64°F | 31°F | 87°F 2010 | 15°F 1935 | 31% | 2% |
| Sep 28 | 63°F | 30°F | 86°F 2010 | 18°F 1945 | 31% | 2% |
| Sep 29 | 62°F | 30°F | 87°F 2024 | 10°F 1985 | 30% | 2% |
| Sep 30 | 62°F | 30°F | 88°F 2024 | 12°F 1985 | 30% | 2% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (MDT).
- September 1
- sunrise 6:47 AM, sunset 8:03 PM
- September 30
- sunrise 7:23 AM, sunset 7:07 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00240775 (Big Sky 2WNW), public domain. Records: NOAA GHCN-Daily, station USC00242793, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.