What is the air quality trend in Chicago?

Over the past 9 days, Chicago had an average AQI of 52 based on station measurements. The worst day was 2026-07-16 with AQI 142.

How is Chicago air quality measured?

Air quality in Chicago 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 Chicago, United States

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

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

Current AQI
Moderate Station

48 Hours 7 Days 14 Days 20 Days

CSV JSON

Air Quality Index Station

125h

PM2.5 Station

125h · 1 station

Temperature GFS model

80pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	Hours	Stations
2026-07-21	33	3–99	9.8 µg/m³	18h	1
2026-07-20	51	23–96	14.2 µg/m³	24h	1
2026-07-19	43	14–85	11.9 µg/m³	24h	1
2026-07-18	13	3–32	3.2 µg/m³	18h	1
2026-07-17	107	22–167	39.3 µg/m³	24h	1
2026-07-16	142	101–188	63.2 µg/m³	11h	1
2026-07-06	36	36–36	8.6 µg/m³	1h	274
2026-07-03	2	2–2	0.4 µg/m³	1h	1
2026-07-02	44	34–54	10.7 µg/m³	4h	69

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