O'Fallon, Illinois Weather
Fireflies pulse through the magnolias. Day 76 of spring. Read this microseason across nine climate regions →
O'Fallon weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Mostly Clear——81°55°—
- ThursdayJun 4Overcast——85°62°+4°
- FridayJun 5Light Drizzle21%—83°64°-2°
- SaturdayJun 6Light Showers20%—88°66°+5°
- SundayJun 7Drizzle33%—88°70°0°
- MondayJun 8Drizzle55%—78°70°-10°
- TuesdayJun 9Drizzle32%—82°70°+4°
Ozone at AQI 61 now. AQI flat over the last 6 hours (within ±3 points). With UV 9.1 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 74 by mid-afternoon.
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 61 now. With UV 9.1 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 74 by mid-afternoon.
- Present
- AQI 61
- UV peak
- 9.1 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 74
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).
The higher the clouds, the finer the weather.
- Moonrise
- 3:46 AM
- Moonset
- 1:04 PM
- In sign
- ♑︎ Capricorn
Fireflies pulse through the magnolias
O'Fallon at a glance
- Today vs. normal: 77°F — typical for the season
- Last frost: April 8 (climatological average for this latitude)
- Microseason: Jun 1–5
- Planting window: Harvest spring lettuce before it bolts. Sow heat-tolerant greens.
Right now in the garden
Peak growing season
As of June 3, 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 General Thunderstorms category for severe thunderstorms day after tomorrow.
- TODAYNONENo severe risk
- TOMORROWNONENo severe risk
- DAY 3TSTMGeneral Thunderstorms
Thunderstorms possible. Not severe, but capable of producing lightning and brief heavy rain.
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.