O'Fallon, Missouri Weather
Dusk arrives one minute earlier each night. Day 43 of summer. Read this microseason across nine climate regions →
O'Fallon weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayAug 2Overcast——82°66°—
- MondayAug 3Clear——85°65°+3°
- TuesdayAug 4Partly Cloudy——87°65°+2°
- WednesdayAug 5Overcast11%—94°67°+7°
- ThursdayAug 6Thunderstorm35%—93°75°-1°
- FridayAug 7Heavy Drizzle26%—95°70°+2°
- SaturdayAug 8Overcast16%—100°73°+5°
AQI 31 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 13.2 µg/m³, PM10 at 13.5 µg/m³ — typical background levels with no transport signature.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion during the projected peak around 10 PM.
What's driving it
Ozone × UV × Sky
Ozone at AQI 41 now. With UV 5.4 peaking around 1 PM under partly cloudy skies, surface ozone likely climbs to AQI 21.
- Present
- AQI 41
- UV peak
- 5.4 at 1 PM
- Sky at peak
- partly cloudy
- Projected peak
- AQI 21
PM × Wind × Precip
PM2.5 at 13.2 µg/m³, PM10 at 13.5 µg/m³ — typical background levels with no transport signature.
- PM2.5/PM10
- 0.98
- Wind
- breezy
- Recent rain
- 0h in last 6h
- Pattern
- background
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).
Red sky at night, sailor's delight.
- Moonrise
- 9:46 PM
- Moonset
- 10:08 AM
- In sign
- ♓︎ Pisces
Dusk arrives one minute earlier each night
O'Fallon at a glance
- Today vs. normal: 10°F above the seasonal normal for this latitude
- Last frost: April 9 (climatological average for this latitude)
- Microseason: Aug 1–5
- Planting window: Sow fall peas. Start kale and collard seedlings for fall.
ZIP codes: 63366, 63368
16-Day Forecast — O'Fallon
- Sun82°66°5%
- Mon85°65°0%
- Tue87°65°0%
- Wed94°67°11%
- Thu93°75°35%
- Fri95°70°26%
- Sat100°73°16%
- Sun100°74°8%
- Mon101°76°9%
- Tue98°75°14%
- Wed102°72°17%
- Thu105°71°30%
- Fri104°73°29%
- Sat95°77°40%
- Sun98°70°20%
- Mon98°70°22%
Forecast data from Open-Meteo (CC BY 4.0).
Live wind & temperature near O'Fallon
Right now in the garden
Peak growing season
As of August 2, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
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.
ZIP codes in O'Fallon
- 63367
- 63366
- 63368