Fairfax Weather in September
Average highs run from 78°F on September 1 to 69°F on September 30, and lows from 55°F to 44°F. Normal precipitation for the month is 3.14 in over about 7 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
- 74°F
- Average low
- 50°F
- Precipitation
- 3.14 in
- Record high
- 105°FSep 10, 1931
- Record low
- 25°FSep 26, 1939
- Chance of a freeze
- 18%
- Days of 90°F or more
- 1.3
- Daylight
- 13 h 13 min to 11 h 45 min
- Cloud cover
- 51%
- Humidity
- 67%
- Dew point
- 50°F
- Wind
- 10.5 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 | 78°F | 55°F | 94°F 1925 | 38°F 1909 | 25% | 0% |
| Sep 2 | 78°F | 55°F | 98°F 1983 | 40°F 1974 | 25% | 0% |
| Sep 3 | 78°F | 55°F | 98°F 2023 | 35°F 1974 | 25% | 0% |
| Sep 4 | 78°F | 54°F | 100°F 1925 | 37°F 1918 | 25% | 0% |
| Sep 5 | 77°F | 54°F | 97°F 1978 | 35°F 1962 | 25% | 0% |
| Sep 6 | 77°F | 54°F | 101°F 1976 | 36°F 1956 | 25% | 0% |
| Sep 7 | 77°F | 53°F | 103°F 1978 | 35°F 1956 | 25% | 0% |
| Sep 8 | 77°F | 53°F | 104°F 1931 | 38°F 1992 | 25% | 0% |
| Sep 9 | 76°F | 53°F | 101°F 1931 | 33°F 1910 | 25% | 0% |
| Sep 10 | 76°F | 52°F | 105°F 1931 | 34°F 1917 | 25% | 0% |
| Sep 11 | 76°F | 52°F | 99°F 1978 | 33°F 1955 | 25% | 0% |
| Sep 12 | 76°F | 52°F | 97°F 1998 | 33°F 2007 | 25% | 0% |
| Sep 13 | 75°F | 51°F | 100°F 1939 | 35°F 1953 | 25% | 0% |
| Sep 14 | 75°F | 51°F | 103°F 1939 | 33°F 1956 | 25% | 0% |
| Sep 15 | 75°F | 50°F | 97°F 1955 | 28°F 2007 | 25% | 0% |
| Sep 16 | 74°F | 50°F | 94°F 1948 | 34°F 1934 | 25% | 0% |
| Sep 17 | 74°F | 50°F | 97°F 1955 | 31°F 1916 | 25% | |
| Sep 18 | 74°F | 49°F | 94°F 1998 | 28°F 1929 | 25% | |
| Sep 19 | 73°F | 49°F | 95°F 1984 | 32°F 1991 | 25% | |
| Sep 20 | 73°F | 48°F | 97°F 2022 | 28°F 1918 | 25% | |
| Sep 21 | 73°F | 48°F | 97°F 1937 | 30°F 2000 | 25% | |
| Sep 22 | 72°F | 48°F | 98°F 1936 | 27°F 1974 | 25% | |
| Sep 23 | 72°F | 47°F | 93°F 1935 | 29°F 1983 | 24% | |
| Sep 24 | 71°F | 47°F | 92°F 1935 | 27°F 1942 | 24% | |
| Sep 25 | 71°F | 46°F | 91°F 1990 | 27°F 1926 | 24% | |
| Sep 26 | 71°F | 46°F | 93°F 1974 | 25°F 1939 | 24% | |
| Sep 27 | 70°F | 45°F | 95°F 1956 | 28°F 1935 | 24% | |
| Sep 28 | 70°F | 45°F | 89°F 2024 | 26°F 1961 | 24% | |
| Sep 29 | 69°F | 45°F | 92°F 2025 | 25°F 1945 | 24% | |
| Sep 30 | 69°F | 44°F | 90°F 1976 | 25°F 1939 | 24% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- September 1
- sunrise 6:42 AM, sunset 7:55 PM
- September 30
- sunrise 7:16 AM, sunset 7:01 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00216839 (Redwood Falls), public domain. Records: NOAA GHCN-Daily, station USW00014992, 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.