Mount Vernon Weather in September
Average highs run from 87°F on September 1 to 76°F on September 30, and lows from 62°F to 51°F. Normal precipitation for the month is 4.70 in over about 8 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
- 82°F
- Average low
- 57°F
- Precipitation
- 4.70 in
- Record high
- 105°FSep 3, 2000
- Record low
- 32°FSep 30, 1984
- Chance of a freeze
- 4%
- Days of 90°F or more
- 5.1
- Daylight
- 12 h 58 min to 11 h 50 min
- Cloud cover
- 45%
- Humidity
- 69%
- Dew point
- 58°F
- Wind
- 7.8 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 | 87°F | 62°F | 103°F 2000 | 51°F 2009 | 25% | 0% |
| Sep 2 | 86°F | 62°F | 103°F 2000 | 48°F 1974 | 25% | 0% |
| Sep 3 | 86°F | 62°F | 105°F 2000 | 42°F 1974 | 25% | 0% |
| Sep 4 | 86°F | 61°F | 101°F 2000 | 40°F 1974 | 25% | 0% |
| Sep 5 | 85°F | 61°F | 103°F 1998 | 45°F 1974 | 25% | 0% |
| Sep 6 | 85°F | 61°F | 103°F 1998 | 44°F 2017 | 25% | 0% |
| Sep 7 | 85°F | 60°F | 100°F 1990 | 45°F 2011 | 25% | 0% |
| Sep 8 | 84°F | 60°F | 99°F 1998 | 45°F 1986 | 25% | 0% |
| Sep 9 | 84°F | 60°F | 99°F 2026 | 48°F 2024 | 25% | 0% |
| Sep 10 | 84°F | 59°F | 99°F 2026 | 44°F 1976 | 26% | 0% |
| Sep 11 | 83°F | 59°F | 95°F 2000 | 44°F 1976 | 26% | 0% |
| Sep 12 | 83°F | 58°F | 97°F 2000 | 46°F 2015 | 26% | 0% |
| Sep 13 | 83°F | 58°F | 93°F 1996 | 45°F 2014 | 26% | 0% |
| Sep 14 | 82°F | 58°F | 98°F 2011 | 43°F 1979 | 26% | 0% |
| Sep 15 | 82°F | 57°F | 96°F 1980 | 40°F 1993 | 26% | 0% |
| Sep 16 | 81°F | 57°F | 98°F 2026 | 42°F 1979 | 26% | 0% |
| Sep 17 | 81°F | 56°F | 98°F 2026 | 40°F 1981 | 26% | 0% |
| Sep 18 | 81°F | 56°F | 97°F 2026 | 35°F 1981 | 26% | 0% |
| Sep 19 | 80°F | 56°F | 93°F 1980 | 38°F 1991 | 26% | 0% |
| Sep 20 | 80°F | 55°F | 94°F 2022 | 40°F 1983 | 27% | 0% |
| Sep 21 | 80°F | 55°F | 94°F 1980 | 33°F 1983 | 27% | 0% |
| Sep 22 | 79°F | 54°F | 95°F 2024 | 37°F 1982 | 27% | 0% |
| Sep 23 | 79°F | 54°F | 93°F 2005 | 38°F 1983 | 26% | 0% |
| Sep 24 | 78°F | 53°F | 93°F 2005 | 38°F 1990 | 26% | 0% |
| Sep 25 | 78°F | 53°F | 89°F 2016 | 38°F 2001 | 26% | 0% |
| Sep 26 | 78°F | 53°F | 88°F 2017 | 37°F 1984 | 26% | 0% |
| Sep 27 | 77°F | 52°F | 87°F 1990 | 39°F 1985 | 26% | 0% |
| Sep 28 | 77°F | 52°F | 88°F 1998 | 42°F 2003 | 26% | 0% |
| Sep 29 | 77°F | 51°F | 89°F 1979 | 36°F 1984 | 26% | 0% |
| Sep 30 | 76°F | 51°F | 89°F 1979 | 32°F 1984 | 26% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- September 1
- sunrise 6:46 AM, sunset 7:44 PM
- September 30
- sunrise 7:10 AM, sunset 7:00 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00235862 (Mt Vernon Univ Mo - Sw Ctr), public domain. Records: NOAA GHCN-Daily, station USC00235704, 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.