Keystone Weather in September
Average highs run from 70°F on September 1 to 61°F on September 30, and lows from 34°F to 25°F. Normal precipitation for the month is 1.40 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
- 66°F
- Average low
- 30°F
- Precipitation
- 1.40 in
- Snowfall
- 1.1 in
- Record high
- 82°FSep 18, 1981
- Record low
- 6°FSep 18, 1971
- Chance of a freeze
- 100%
- Daylight
- 13 h 03 min to 11 h 49 min
- Cloud cover
- 50%
- Humidity
- 57%
- Dew point
- 28°F
- Wind
- 4.7 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 | 70°F | 34°F | 73°F 2019 | 26°F 1956 | 40% | 1% |
| Sep 2 | 70°F | 33°F | 79°F 1981 | 25°F 1973 | 39% | 1% |
| Sep 3 | 70°F | 33°F | 78°F 1981 | 21°F 1961 | 39% | 1% |
| Sep 4 | 70°F | 33°F | 78°F 1997 | 20°F 2008 | 38% | 1% |
| Sep 5 | 69°F | 33°F | 72°F 1995 | 21°F 1968 | 38% | 1% |
| Sep 6 | 69°F | 32°F | 74°F 1998 | 26°F 1956 | 38% | 1% |
| Sep 7 | 69°F | 32°F | 74°F 1978 | 20°F 2001 | 38% | 1% |
| Sep 8 | 69°F | 32°F | 72°F 1979 | 20°F 1993 | 37% | 1% |
| Sep 9 | 68°F | 32°F | 71°F 1981 | 13°F 2020 | 37% | 1% |
| Sep 10 | 68°F | 31°F | 70°F 2021 | 16°F 2020 | 37% | 1% |
| Sep 11 | 68°F | 31°F | 71°F 2021 | 16°F 2020 | 36% | 1% |
| Sep 12 | 68°F | 31°F | 68°F 2021 | 16°F 2020 | 36% | 2% |
| Sep 13 | 67°F | 31°F | 70°F 1981 | 19°F 1967 | 35% | 2% |
| Sep 14 | 67°F | 30°F | 71°F 1990 | 10°F 1993 | 35% | 2% |
| Sep 15 | 67°F | 30°F | 73°F 2018 | 12°F 1993 | 34% | 2% |
| Sep 16 | 66°F | 30°F | 76°F 2018 | 10°F 1994 | 34% | 2% |
| Sep 17 | 66°F | 29°F | 70°F 2018 | 14°F 2006 | 33% | 2% |
| Sep 18 | 66°F | 29°F | 82°F 1981 | 6°F 1971 | 33% | 2% |
| Sep 19 | 65°F | 29°F | 72°F 2018 | 8°F 1971 | 32% | 3% |
| Sep 20 | 65°F | 29°F | 75°F 2010 | 10°F 1978 | 32% | 3% |
| Sep 21 | 65°F | 28°F | 66°F 2014 | 8°F 1895 | 31% | 3% |
| Sep 22 | 64°F | 28°F | 72°F 1980 | 10°F 1995 | 31% | 3% |
| Sep 23 | 64°F | 28°F | 68°F 1992 | 8°F 1985 | 30% | 4% |
| Sep 24 | 64°F | 27°F | 67°F 1978 | 9°F 1985 | 30% | 4% |
| Sep 25 | 63°F | 27°F | 69°F 2015 | 10°F 1961 | 30% | 4% |
| Sep 26 | 63°F | 27°F | 69°F 2019 | 11°F 1970 | 29% | 4% |
| Sep 27 | 62°F | 26°F | 68°F 2010 | 8°F 1996 | 29% | 5% |
| Sep 28 | 62°F | 26°F | 69°F 2001 | 11°F 1999 | 29% | 5% |
| Sep 29 | 62°F | 26°F | 68°F 2010 | 10°F 1973 | 28% | 5% |
| Sep 30 | 61°F | 25°F | 70°F 2010 | 8°F 1959 | 28% | 5% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (MDT).
- September 1
- sunrise 6:32 AM, sunset 7:35 PM
- September 30
- sunrise 6:59 AM, sunset 6:48 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00052281 (Dillon 1 E), public domain. Records: NOAA GHCN-Daily, station USC00051660, 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.