O'Fallon Weather in August
Average highs run from 90°F on August 1 to 87°F on August 31, and lows from 67°F to 62°F. Normal precipitation for the month is 3.92 in over about 7 wet days.
August day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
August at a glance
- Average high
- 89°F
- Average low
- 65°F
- Precipitation
- 3.92 in
- Record high
- 105°FAug 15, 2007
- Record low
- 39°FAug 29, 1986
- Chance of a freeze
- 0%
- Days of 90°F or more
- 14.4
- Daylight
- 14 h 09 min to 13 h 03 min
- Cloud cover
- 47%
- Humidity
- 71%
- Dew point
- 65°F
- Wind
- 6.0 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 |
|---|---|---|---|---|---|---|
| Aug 1 | 90°F | 67°F | 100°F 1980 | 50°F 1971 | 24% | 0% |
| Aug 2 | 90°F | 67°F | 100°F 1964 | 53°F 1977 | 24% | 0% |
| Aug 3 | 90°F | 67°F | 104°F 1964 | 51°F 1965 | 24% | 0% |
| Aug 4 | 90°F | 67°F | 101°F 1954 | 49°F 1976 | 24% | 0% |
| Aug 5 | 90°F | 67°F | 100°F 1956 | 52°F 1974 | 24% | 0% |
| Aug 6 | 90°F | 67°F | 99°F 1983 | 50°F 1997 | 24% | 0% |
| Aug 7 | 90°F | 67°F | 100°F 2007 | 46°F 1990 | 24% | 0% |
| Aug 8 | 90°F | 67°F | 101°F 2007 | 46°F 1989 | 24% | 0% |
| Aug 9 | 90°F | 67°F | 101°F 2007 | 46°F 1989 | 24% | 0% |
| Aug 10 | 90°F | 67°F | 100°F 1980 | 46°F 1989 | 24% | 0% |
| Aug 11 | 90°F | 66°F | 100°F 2005 | 47°F 1989 | 23% | 0% |
| Aug 12 | 90°F | 66°F | 101°F 2007 | 45°F 1967 | 23% | 0% |
| Aug 13 | 90°F | 66°F | 101°F 2007 | 46°F 1964 | 23% | 0% |
| Aug 14 | 90°F | 66°F | 100°F 2007 | 46°F 2004 | 23% | 0% |
| Aug 15 | 89°F | 66°F | 105°F 2007 | 46°F 2004 | 23% | 0% |
| Aug 16 | 89°F | 66°F | 105°F 2007 | 48°F 2004 | 23% | 0% |
| Aug 17 | 89°F | 65°F | 100°F 1988 | 52°F 1994 | 23% | 0% |
| Aug 18 | 89°F | 65°F | 101°F 1954 | 50°F 1989 | 23% | 0% |
| Aug 19 | 89°F | 65°F | 103°F 1962 | 51°F 1977 | 23% | 0% |
| Aug 20 | 89°F | 65°F | 103°F 1962 | 48°F 1967 | 22% | 0% |
| Aug 21 | 89°F | 65°F | 101°F 2003 | 46°F 1967 | 22% | 0% |
| Aug 22 | 89°F | 64°F | 100°F 2003 | 47°F 2024 | 22% | 0% |
| Aug 23 | 89°F | 64°F | 100°F 2007 | 51°F 1997 | 22% | 0% |
| Aug 24 | 88°F | 64°F | 100°F 2007 | 50°F 1966 | 22% | 0% |
| Aug 25 | 88°F | 64°F | 98°F 2011 | 50°F 1966 | 22% | 0% |
| Aug 26 | 88°F | 64°F | 99°F 1983 | 50°F 1970 | 22% | 0% |
| Aug 27 | 88°F | 63°F | 99°F 1983 | 49°F 1967 | 22% | 0% |
| Aug 28 | 88°F | 63°F | 100°F 1990 | 43°F 1967 | 22% | 0% |
| Aug 29 | 88°F | 63°F | 99°F 1990 | 39°F 1986 | 22% | 0% |
| Aug 30 | 87°F | 62°F | 98°F 1951 | 41°F 1986 | 22% | 0% |
| Aug 31 | 87°F | 62°F | 99°F 1951 | 44°F 1988 | 22% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- August 1
- sunrise 6:01 AM, sunset 8:10 PM
- August 31
- sunrise 6:28 AM, sunset 7:31 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USW00013802 (Belleville Siu Rsch), public domain. Records: NOAA GHCN-Daily, station USW00013802, 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.