What is the air quality trend in St. Charles?

Over the past 8 days, St. Charles had an average AQI of 78 based on station measurements. The worst day was 2026-07-17 with AQI 168.

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
Good Station

48 Hours 7 Days 14 Days 20 Days

CSV JSON

Air Quality Index Station

166h

PM2.5 Station

166h · 33 stations

Temperature GFS model

28pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	Hours	Stations
2026-07-22	21	16–27	5.0 µg/m³	5h	31
2026-07-21	53	28–74	14.5 µg/m³	24h	29
2026-07-20	68	42–80	20.2 µg/m³	24h	29
2026-07-19	63	38–91	18.3 µg/m³	24h	31
2026-07-18	129	58–157	49.5 µg/m³	24h	30
2026-07-17	168	59–226	99.0 µg/m³	24h	32
2026-07-16	76	40–145	23.7 µg/m³	24h	30
2026-07-15	51	42–60	12.9 µg/m³	17h	31

Back to St. Charles Air Quality