Worst air pollution St. Charles, Missouri, today and tomorrow
Today (20 September): Air quality in St. Charles, Missouri is fair. AQI, PM2.5, and O3 are fair; PM10, NO2, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 6:00 PM (PM2.5: 26.6/100).
Tomorrow (21 September 2026): Air quality in St. Charles, Missouri is fair. NO2 increases to fair; all other pollutants stay as today. Pollution peaks around 5:00 AM (O3: 29.3/100). Airmine updates local air quality forecasts four times daily.
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Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team
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St. Charles' air quality reflects the Missouri River valley's flat terrain west of St. Louis, with vehicle emissions from I-70 and the surrounding suburban and commercial character contributing local sources. The Missouri River corridor channels prevailing westerly winds, while summer ozone from regional agricultural and vehicle sources across the broader Midwest airshed is the primary warm-season concern and the flat river plain generally allows reasonable dispersal throughout the year.
Today - 20 September | Pollution peaks at 18:00
AQI:
Fair
26.6/100
PM2.5 (fine particles):
Fair
26.6/100
PM10 (coarse particles):
Good
14.7/100
NO2 (nitrogen dioxide):
Good
13.2/100
O3 (ozone):
Fair
26.1/100
SO2 (sulfur dioxide):
Good
1.3/100
CO (carbon monoxide):
Good
0.6/100
HCHO (formaldehyde):
Good
3.2/100
PM1 (ultrafine particles):
Good
3.5/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 05:00
AQI:
Fair
29.3/100
PM2.5 (fine particles):
Fair
26.7/100
PM10 (coarse particles):
Good
14.7/100
NO2 (nitrogen dioxide):
Fair
20.5/100
O3 (ozone):
Fair
29.3/100
SO2 (sulfur dioxide):
Good
1.2/100
CO (carbon monoxide):
Good
0.6/100
HCHO (formaldehyde):
Good
3.6/100
PM1 (ultrafine particles):
Good
3.9/100
Pollen forecast in St. Charles, Missouri
View pollen forecastFrequently Asked Questions
Is air quality bad in St. Charles, Missouri right now?
On 20 September 2026, overall air quality in St. Charles, Missouri is fair. AQI is the main air quality indicator at 26.6/100. Pollution peaks around 6:00 PM (PM2.5: 26.6/100).
Will air quality be worse tomorrow in St. Charles, Missouri?
On 21 September 2026, air quality conditions in St. Charles, Missouri will be similar to today, with AQI forecast at fair at 29.3/100. Pollution peaks around 5:00 AM (O3: 29.3/100).
When is air pollution at its worst in St. Charles, Missouri?
Air quality in St. Charles shifts across the year. Typically, the calmest air usually arrives in winter, between planting and harvest dust events, while spring planting and autumn harvest can push particulate levels up with dust and agricultural burning. Wide-open terrain generally helps disperse pollution quickly once the wind picks up.
Are air quality levels in St. Charles, Missouri based on measurements or forecasts?
It is forecasts derived by downscaling forecasts provided by EU’s Copernicus Atmosphere Monitoring Service (CAMS) by taking into account local conditions such as traffic patterns. CAMS bases its forecast on satellite measurements of particles and chemical compounds in the atmosphere. Airmine’s services were developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team.
Why doesn’t the forecast always reflect wildfire impacts?
Airmine’s forecast uses CAMS (Copernicus Atmosphere Monitoring Service) as its background atmospheric model. While CAMS includes wildfire emissions, these are derived from satellite observations and are not available in real time. During rapidly evolving wildfire events, there may therefore be a delay before increased emissions are incorporated into the model. As a result, the forecast may temporarily underestimate PM₂.₅ and other pollutants associated with wildfire smoke.
During rapidly evolving wildfire events, CAMS may lag by approximately 1–2 days before increased wildfire emissions are fully represented, which can lead to temporary underestimation of PM₂.₅ concentrations in Airmine’s forecast.
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Data provided by Airmine — Last update: 20 September 2026 at 14:33 CEST (Data is updated four times daily.)
This forecast is produced independently using Airmine's own atmospheric data and models.
Unless explicitly made clear, the content on this site has not been paid for by external organisations and is Airmine's sole responsibility.
Disclaimer: Forecasts are provided for informational purposes only and should not be relied upon as medical advice. Actual pollen and air quality conditions may vary from the forecast. If you have allergies, asthma, or another medical condition, consult a healthcare professional. Please see our Terms of Service for important information about limitations of liability.
Some text on this page may be generated or summarised using artificial intelligence (AI). Wherever possible, AI-generated content is enriched with Airmine's proprietary data to improve its accuracy and relevance. However, AI-generated content may still contain errors, omissions, or inaccuracies.
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