What is the air quality trend in St. Charles?

Over the past 8 days, St. Charles had an average AQI of 31 based on station measurements. The worst day was 2026-10-21 with AQI 56.

How is St. Charles air quality measured?

Air quality in St. Charles is measured by ground-level monitoring stations that report PM2.5 and PM10 concentrations hourly. CERNS.IO aggregates readings from nearby stations and converts PM2.5 to the US EPA Air Quality Index (AQI) scale.

Air Quality History for St. Charles, United States

Name: St. Charles Air Quality History
Creator: CERNS.IO
License: https://creativecommons.org/licenses/by/4.0/

Historical PM2.5 and AQI trend from monitoring stations near St. Charles, United States.

Current AQI
Moderate Station

48 Hours 7 Days 14 Days 20 Days

CSV JSON

Air Quality Index Station

165h

PM2.5 Station

165h · 110 stations

Temperature GFS model

28pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	PM10 avg	Hours	Stations
2026-10-21	56	52–60	14.8 µg/m³	1.0	4h	108
2026-10-20	52	29–70	13.6 µg/m³	—	24h	95
2026-10-19	28	22–42	6.6 µg/m³	—	24h	108
2026-10-18	24	18–37	5.7 µg/m³	—	24h	100
2026-10-17	16	13–24	4.0 µg/m³	—	24h	107
2026-10-16	18	12–35	4.4 µg/m³	—	24h	102
2026-10-15	24	14–40	5.8 µg/m³	—	24h	107
2026-10-14	34	19–51	8.2 µg/m³	1.1	17h	107

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