St. Charles, Missouri Weather
Fireflies pulse through the magnolias. Day 77 of spring. Read this microseason across nine climate regions →
St. Charles weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——86°60°—
- FridayJun 5Overcast14%—85°68°-1°
- SaturdayJun 6Light Drizzle27%—87°67°+2°
- SundayJun 7Light Showers48%—83°71°-4°
- MondayJun 8Showers61%0.04″84°70°+1°
- TuesdayJun 9Thunderstorm40%—89°69°+5°
- WednesdayJun 10Thunderstorm22%—92°70°+3°
Ozone at AQI 42. AQI down 42 over the last 6 hours — air quality is improving sharply. Overcast through the UV peak window (cloud cover ~100%) — afternoon ozone should stay flat.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion during the projected peak around 7 AM.
What's driving it
Ozone × UV × Sky
Ozone at AQI 42. Overcast through the UV peak window (cloud cover ~100%) — afternoon ozone should stay flat.
- Present
- AQI 42
- UV peak
- 3.3 at 1 PM
- Sky at peak
- overcast
- Projected peak
- AQI 9
PM × Wind × Precip
PM2.5 at 4.7 µg/m³ (AQI 26) with a 0.96 fine-to-coarse ratio and 6 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.96
- 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).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 4:27 AM
- Moonset
- 2:08 PM
- In sign
- ♑︎ Capricorn
Fireflies pulse through the magnolias
St. Charles at a glance
- Today vs. normal: 13°F below the seasonal normal for this latitude
- Last frost: April 9 (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 General Thunderstorms category for severe thunderstorms tomorrow.
- TODAYNONENo severe risk
- TOMORROWTSTMGeneral Thunderstorms
- 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.