O'Fallon, Missouri Weather
Camellia Blooms Break Through. Day 50 of autumn. Read this microseason across nine climate regions →
O'Fallon weather forecast — hour by hour, 7-day outlook, NOAA radar
Conditions updated 1:31 PM CST · Open-Meteo
- TodayNov 10Clear——68°45°—
- WednesdayNov 11Clear——64°46°-4°
- ThursdayNov 12Overcast——55°36°-9°
- FridayNov 13Clear——47°31°-8°
- SaturdayNov 14Partly Cloudy——47°28°0°
- SundayNov 15Overcast10%—49°30°+2°
- MondayNov 16Overcast10%—52°33°+3°
Air quality now AQI 23 · Good
AQI 23 (Good), driven by Ozone. Ozone at AQI 31 now. With UV 2.5 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 10.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 31 now. With UV 2.5 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 10.
- Present
- AQI 31
- UV peak
- 2.5 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 10
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
When the wind is in the west, the weather is at its best.
- Moonrise
- 8:19 AM
- Moonset
- 5:33 PM
- In sign
- ♐︎ Sagittarius
Camellia Blooms Break Through
Read this microseason across nine climate regions →
All 72 microseasons on the year wheel →
O'Fallon at a glance
- Today vs. normal: Today averages 57°F (high 68°F, low 45°F), 10°F above the 47°F normal for Nov 10
- Last frost: April 10 (1991–2020 median, NOAA station 10 km away)
- Microseason: Nov 6–10
- Planting calendar: November — harvest fall brassicas, carrots
16-Day Forecast — O'Fallon
- Tue68°45°0%
- Wed64°46°1%
- Thu55°36°1%
- Fri47°31°0%
- Sat47°28°0%
- Sun49°30°10%
- Mon52°33°10%
- Tue53°33°1%
- Wed58°37°6%
- Thu60°47°13%
- Fri58°54°17%
- Sat65°39°42%
- Sun39°23°32%
- Mon30°20°16%
- Tue36°19°10%
- Wed54°25°13%
Forecast data from Open-Meteo (CC BY 4.0).
Live wind & temperature near O'Fallon
Interactive wind and temperature map centered on O'Fallon — it loads in your browser. Open the full weather map.
Right now in the garden
Post-frost dormancy
As of November 10, the season's first frost (typically October 26) is due or past. Bring frost-tender plants indoors, mulch overwintering beds, and turn spent plantings under. This city's planting calendar for November: harvest fall brassicas and carrots.
Sun & seasons in O'Fallon
O'Fallon sits in St. Charles County, where the year’s longest day runs 14h 53m of daylight and its shortest just 9h 27m — a swing of +5h 26m between the June and December solstices. Clocks spring forward on Sunday, March 8, 2026 and fall back on Sunday, November 1, 2026.
St. Louis, the state’s largest city, lies about 27 miles to the ESE. The nearest town O'Fallon tracks is St. Louis, roughly 27 miles to the ESE.
Air quality in O'Fallon
Air quality in O'Fallon’s county has trended dirtier since 2020; its cleanest year on record was 2020 (median AQI 39).
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| March | lettuce, peas, spinach, radishes | — |
| April | lettuce, peas, spinach, radishes | spinach, radishes |
| May | tomatoes, peppers, beans, squash | lettuce, peas, spinach, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, spinach, beans, summer squash, garlic |
| July | tomatoes, peppers, beans, squash | tomatoes, peppers, beans, summer squash, garlic |
| August | beans, squash, fall brassicas, carrots | tomatoes, peppers, beans, summer squash, winter squash |
| September | garlic (overwinter) | tomatoes, peppers, beans, summer squash, winter squash |
| October | garlic (overwinter) | tomatoes, peppers, beans, summer squash, winter squash, fall brassicas, carrots |
| November | — | fall brassicas, carrots |
A year in weather
O'Fallon's warmest month is July (~77°F mean) and its coldest is January (~30°F). Rainfall peaks in May (5.1 inches) and bottoms out in February (2.4 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 30° | 2.6″ | 8 |
| February | 35° | 2.4″ | 8 |
| March | 44° | 3.7″ | 10 |
| April | 55° | 4.7″ | 10 |
| May | 65° | 5.1″ | 13 |
| June | 74° | 4.7″ | 10 |
| July | 77° | 3.9″ | 8 |
| August | 76° | 3.6″ | 8 |
| September | 68° | 3.5″ | 7 |
| October | 57° | 3.4″ | 9 |
| November | 45° | 3.7″ | 8 |
| December | 35° | 3.1″ | 8 |
Regional context
Similar climates Dardenne Prairie, MO, Lake St. Louis, MO, Cottleville, MO
Per NOAA NCEI 1991-2020 normals, O'Fallon runs from a 30°F January mean to 77°F in July, a 47°F seasonal spread, with near 44.4 inches of precipitation across about 107 wet days.
Rainfall in O'Fallon splits evenly between the seasons: May tops out at 5.1 inches over 12.6 rainy days, and February logs 2.4 inches across 8.2 — neither half of O'Fallon's year dominates. That lines O'Fallon up with places like Dardenne Prairie, MO, Lake St. Louis, MO and Cottleville, MO, fed by overlapping storm tracks.
Once O'Fallon passes April 10, freezes fade and O'Fallon's beds take peas, lettuce, spinach, and radishes. Tomatoes and peppers do best set out two weeks later in O'Fallon, once nights clear the mid-40s°F. The season ends by October 26 in O'Fallon, once hard frosts set back in. That date is a median: O'Fallon freezes sooner in half of years.
Similar climates: Dardenne Prairie, MO, Lake St. Louis, MO, Cottleville, MO, St. Paul, MO, Josephville, MO.
Frequently asked
- When does it freeze in O'Fallon?
- In O'Fallon, expect the last spring frost near April 10; O'Fallon's first autumn frost comes around October 26.
- What is the rainy season in O'Fallon?
- O'Fallon sees its heaviest rain in May (around 5.1 inches), part of roughly 44 inches a year.
- What is the warmest month in O'Fallon?
- The warmest stretch in O'Fallon comes in July, around 77°F on average.
- What is the coldest month in O'Fallon?
- On average January is the chilliest month in O'Fallon, about 30°F.
- When can I start a vegetable garden in O'Fallon?
- O'Fallon's last frost (April 10) cues hardy greens; in O'Fallon, hold heat-lovers two weeks past.
- How many rainy days does O'Fallon get?
- O'Fallon records around 107 days of measurable precipitation annually.
- What hardiness zone is O'Fallon?
- O'Fallon's USDA zone comes from its January mean (30°F); enter the ZIP on the USDA lookup for the number.
- What is the 10-day forecast for O'Fallon?
- O'Fallon's extended outlook — daily high and low temperatures and precipitation chances for each upcoming day — is in the daily forecast above.
- Will it rain this week in O'Fallon?
- See this week's day-by-day rain chances for O'Fallon in the daily forecast above, and the next 24 hours in the hourly chart.
- What is the weather like right now in O'Fallon?
- Current conditions for O'Fallon and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
- How often is the O'Fallon forecast updated?
- The O'Fallon forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
- When are sunrise and sunset in O'Fallon?
- Today's sunrise and sunset times for O'Fallon are in the Almanac section above, along with civil dawn, civil dusk, and day length. Day length is longest near the summer solstice and shortest near the winter solstice.
- How accurate is the weather forecast for O'Fallon?
- The next few days in O'Fallon's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.
O'Fallon sits at 38.8°N; its climate zone is humid subtropical (Köppen approximation).
ZIP codes in O'Fallon
- 63366
- 63367
- 63368