SmogRank / World / North America / United States / Illinois
Most polluted cities in Illinois, United States
37 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Granite City at 8.7 µg/m³, #848 in the world.
About 0 people in these 3 cities breathed unhealthy air on an average day over the last 30 days.
Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.
Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Estimated: cities without a monitor
Illinois cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.
| City | 7-day estimate |
|---|---|
| Aurora | ≈ 7 µg/m³ |
| North Peoria | ≈ 7 µg/m³ |
| Waukegan | ≈ 6 µg/m³ |
| Cicero | ≈ 8 µg/m³ |
| Arlington Heights | ≈ 8 µg/m³ |
| Schaumburg | ≈ 8 µg/m³ |
| Bolingbrook | ≈ 7 µg/m³ |
| Palatine | ≈ 8 µg/m³ |
| Orland Park | ≈ 7 µg/m³ |
| Tinley Park | ≈ 7 µg/m³ |
| Berwyn | ≈ 8 µg/m³ |
| Mount Prospect | ≈ 8 µg/m³ |
| Normal | ≈ 5 µg/m³ |
| Wheaton | ≈ 8 µg/m³ |
| Oak Park | ≈ 8 µg/m³ |
| Hoffman Estates | ≈ 8 µg/m³ |
| Downers Grove | ≈ 8 µg/m³ |
| Glenview | ≈ 7 µg/m³ |
| Elmhurst | ≈ 8 µg/m³ |
| Lombard | ≈ 8 µg/m³ |
| DeKalb | ≈ 6 µg/m³ |
| Plainfield | ≈ 7 µg/m³ |
| Urbana | ≈ 6 µg/m³ |
| Belleville | ≈ 9 µg/m³ |
| Bartlett | ≈ 8 µg/m³ |
| Buffalo Grove | ≈ 8 µg/m³ |
| Quincy | ≈ 6 µg/m³ |
| Streamwood | ≈ 8 µg/m³ |
| Crystal Lake | ≈ 6 µg/m³ |
| Carol Stream | ≈ 8 µg/m³ |
| Romeoville | ≈ 7 µg/m³ |
| Rock Island | ≈ 7 µg/m³ |
| Carpentersville | ≈ 7 µg/m³ |
| Hanover Park | ≈ 8 µg/m³ |
| Wheeling | ≈ 8 µg/m³ |
| Addison | ≈ 8 µg/m³ |
| Glendale Heights | ≈ 8 µg/m³ |
| Oswego | ≈ 7 µg/m³ |
| Woodridge | ≈ 7 µg/m³ |
| Elk Grove Village | ≈ 8 µg/m³ |
Bad-air episodes in Illinois
- Northern United States and Canada, July 202614 to 21 July 2026, 8 days327 cities548 µg/m³peak, Superior
- North-eastern United States, June and July 202630 June to 2 July 2026, 3 days38 cities32 µg/m³peak, Westerville
- North-eastern United States and Canada, March 20264 to 5 March 2026, 2 days40 cities38 µg/m³peak, Hamilton
- North-eastern United States and Canada, 14 to 19 February 20266 days108 cities54 µg/m³peak, Lancaster
- North-eastern United States and Canada around Milwaukee, 6 January 20261 day21 cities41 µg/m³peak, Royal Oak
- Northern United States, December 202524 to 25 December 2025, 2 days11 cities33 µg/m³peak, Wheaton
Times when many cities around here had PM2.5 at twice their usual or more on the same days.
Use this board
SmogRank, most polluted cities in Illinois, United States, PM2.5, last 30 days to 6 Oct 2026, 22:00 UTC, smogrank.com/us/region/illinois?w=30d.
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Updated 2026-10-06 22:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.