St. Charles, Illinois Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
St. Charles weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Partly Cloudy——83°49°—
- ThursdayJun 4Overcast——86°57°+3°
- FridayJun 5Heavy Drizzle74%0.02″79°67°-7°
- SaturdayJun 6Showers55%0.73″81°63°+2°
- SundayJun 7Light Drizzle12%—81°66°0°
- MondayJun 8Light Showers38%0.02″78°66°-3°
- TuesdayJun 9Light Drizzle29%—83°70°+5°
PM2.5 at 9.1 µg/m³ (AQI 51) with a 0.88 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust. AQI down 10 over the last 6 hours (steady decline since this morning).
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 0.0 peaking around 1 PM under partly cloudy skies, surface ozone likely climbs to AQI 5 by mid-afternoon.
- Present
- AQI 31
- UV peak
- 0.0 at 1 PM
- Sky at peak
- partly cloudy
- Projected peak
- AQI 5
PM × Wind × Precip
PM2.5 at 9.1 µg/m³ (AQI 51) with a 0.88 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.88
- Wind
- calm
- 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).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 4:29 AM
- Moonset
- 1:49 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
St. Charles at a glance
- Today vs. normal: 10°F below the seasonal normal for this latitude
- Last frost: April 28 (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 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 — St. Charles
SPC has placed St. Charles in the Marginal Risk category for severe thunderstorms day after tomorrow.
- TODAYNONENo severe risk
- TOMORROWNONENo severe risk
- DAY 3MRGLMarginal Risk
Isolated severe storms possible. Limited threat for hail or damaging wind.
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.