What is the air quality trend in Saint Charles?

Over the past 8 days, Saint Charles had an average AQI of 79 based on station measurements. The worst day was 2026-07-17 with AQI 169.

How is Saint Charles air quality measured?

Air quality in Saint 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 Saint Charles, United States

Name: Saint 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 Saint Charles, United States.

Current AQI
Good Station

48 Hours 7 Days 14 Days 20 Days

CSV JSON

Air Quality Index Station

166h

PM2.5 Station

166h · 31 stations

Temperature GFS model

28pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	Hours	Stations
2026-07-22	20	16–26	4.9 µg/m³	5h	29
2026-07-21	53	28–75	14.7 µg/m³	24h	28
2026-07-20	69	51–80	20.6 µg/m³	24h	28
2026-07-19	63	38–91	18.4 µg/m³	24h	30
2026-07-18	129	58–158	50.3 µg/m³	24h	29
2026-07-17	169	59–226	100.5 µg/m³	24h	31
2026-07-16	77	42–149	24.2 µg/m³	24h	29
2026-07-15	52	42–62	13.0 µg/m³	17h	30

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