O'Fallon Weather in December
Average highs run from 51°F on December 1 to 43°F on December 31, and lows from 32°F to 25°F. Normal precipitation for the month is 2.61 in over about 8 wet days.
December day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
December at a glance
- Average high
- 46°F
- Average low
- 28°F
- Precipitation
- 2.61 in
- Snowfall
- 2.9 in
- Record high
- 78°FDec 28, 2025
- Record low
- -19°FDec 22, 1989
- Chance of a freeze
- 100%
- Daylight
- 9 h 40 min to 9 h 31 min
- Cloud cover
- 66%
- Humidity
- 82%
- Dew point
- 29°F
- Wind
- 9.2 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 |
|---|---|---|---|---|---|---|
| Dec 1 | 51°F | 32°F | 75°F 1970 | 11°F 2002 | 25% | 4% |
| Dec 2 | 51°F | 32°F | 75°F 2012 | 11°F 1985 | 25% | 4% |
| Dec 3 | 50°F | 31°F | 76°F 1970 | 12°F 1976 | 25% | 4% |
| Dec 4 | 50°F | 31°F | 77°F 2021 | 11°F 1991 | 25% | 4% |
| Dec 5 | 50°F | 31°F | 71°F 1956 | 10°F 2025 | 25% | 4% |
| Dec 6 | 49°F | 31°F | 68°F 1951 | 5°F 1977 | 25% | 5% |
| Dec 7 | 49°F | 30°F | 71°F 1966 | 5°F 1950 | 25% | 5% |
| Dec 8 | 48°F | 30°F | 68°F 1966 | 8°F 2006 | 25% | 5% |
| Dec 9 | 48°F | 30°F | 66°F 1965 | -2°F 2005 | 25% | 5% |
| Dec 10 | 48°F | 30°F | 68°F 2020 | 1°F 1995 | 25% | 5% |
| Dec 11 | 47°F | 29°F | 72°F 1949 | 2°F 1962 | 25% | 5% |
| Dec 12 | 47°F | 29°F | 72°F 2015 | -7°F 1962 | 25% | 5% |
| Dec 13 | 47°F | 29°F | 69°F 1948 | -1°F 1962 | 25% | 6% |
| Dec 14 | 47°F | 29°F | 67°F 2006 | 0°F 1985 | 25% | 6% |
| Dec 15 | 46°F | 28°F | 75°F 1948 | -2°F 1989 | 25% | 6% |
| Dec 16 | 46°F | 28°F | 69°F 1984 | -14°F 1989 | 25% | 6% |
| Dec 17 | 46°F | 28°F | 66°F 1984 | -12°F 1989 | 25% | 6% |
| Dec 18 | 45°F | 28°F | 65°F 1984 | -5°F 1963 | 24% | 6% |
| Dec 19 | 45°F | 28°F | 66°F 1976 | -5°F 1963 | 24% | 6% |
| Dec 20 | 45°F | 27°F | 69°F 1988 | -15°F 1989 | 24% | 6% |
| Dec 21 | 45°F | 27°F | 64°F 1949 | -6°F 1989 | 24% | 7% |
| Dec 22 | 44°F | 27°F | 65°F 1965 | -19°F 1989 | 24% | 7% |
| Dec 23 | 44°F | 27°F | 71°F 2025 | -16°F 1989 | 24% | 7% |
| Dec 24 | 44°F | 27°F | 69°F 1955 | -14°F 1989 | 24% | 7% |
| Dec 25 | 44°F | 26°F | 70°F 2025 | -9°F 1983 | 24% | 7% |
| Dec 26 | 44°F | 26°F | 73°F 2025 | 0°F 1948 | 24% | 7% |
| Dec 27 | 44°F | 26°F | 69°F 1971 | 3°F 2017 | 23% | 7% |
| Dec 28 | 43°F | 26°F | 78°F 2025 | -1°F 2000 | 23% | 7% |
| Dec 29 | 43°F | 26°F | 69°F 1984 | -4°F 1983 | 23% | 7% |
| Dec 30 | 43°F | 26°F | 68°F 1965 | -8°F 1983 | 23% | 7% |
| Dec 31 | 43°F | 25°F | 72°F 1951 | -6°F 1976 | 23% | 7% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CST).
- December 1
- sunrise 6:59 AM, sunset 4:39 PM
- December 31
- sunrise 7:17 AM, sunset 4:48 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.