O'Fallon, Missouri Weather
Cicadas claim the scorching afternoon. Day 14 of summer. Read this microseason across nine climate regions →
O'Fallon weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 4Light Rain18%0.11″93°75°—
- SundayJul 5Heavy Rain19%2.0″81°71°-12°
- MondayJul 6Overcast14%—85°68°+4°
- TuesdayJul 7Overcast——84°67°-1°
- WednesdayJul 8Overcast——93°66°+9°
- ThursdayJul 9Light Drizzle32%—92°72°-1°
- FridayJul 10Drizzle42%0.01″90°74°-2°
AQI 50 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 11.3 µg/m³ (AQI 55) with a 0.92 fine-to-coarse ratio and 6 mph wind — combustion smoke trapped in calm air, not road dust.
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 37. Overcast through the UV peak window (cloud cover ~100%) — afternoon ozone should stay flat.
- Present
- AQI 37
- UV peak
- 5.7 at 1 PM
- Sky at peak
- overcast
- Projected peak
- AQI 14
PM × Wind × Precip
PM2.5 at 11.3 µg/m³ (AQI 55) with a 0.92 fine-to-coarse ratio and 6 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.92
- Wind
- light
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
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).
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
- Moonrise
- 10:55 PM
- Moonset
- 10:10 AM
- In sign
- ♓︎ Pisces
Cicadas claim the scorching afternoon
O'Fallon at a glance
- Today vs. normal: 15°F above the seasonal normal for this latitude
- Last frost: April 9 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
ZIP codes: 63366, 63368
16-Day Forecast — O'Fallon
- Sat93°75°18%
- Sun81°71°19%
- Mon85°68°14%
- Tue84°67°5%
- Wed93°66°6%
- Thu92°72°32%
- Fri90°74°42%
- Sat86°73°22%
- Sun78°61°7%
- Mon79°57°7%
- Tue80°60°10%
- Wed82°65°13%
- Thu84°66°13%
- Fri82°68°19%
- Sat85°70°17%
- Sun87°72°14%
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 July 4, 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.
SPC Convective Outlook
Storm Prediction Center — O'Fallon
SPC has placed O'Fallon in the Slight Risk category for severe thunderstorms today.
- TODAYSLGTSlight Risk
- TOMORROWTSTMGeneral Thunderstorms
- DAY 3TSTMGeneral Thunderstorms
Scattered severe storms possible. A few tornadoes, hail, and damaging wind gusts possible.
Source: NOAA / NWS Storm Prediction Center categorical convective outlook. Outlooks are re-issued multiple times per day; this page reflects the most recent SPC polygons covering the city’s coordinates.
ZIP codes in O'Fallon
- 63367
- 63366
- 63368