SmogRank / World / United States / Illinois / January 2023

Most unhealthy days in Illinois, United States, January 2023

19 cities in Illinois, United States ranked by their share of unhealthy days over the 31 days. The most unhealthy days: Granite City, United States, 0 of 22 measured days. A city needs measurements on 70% of the days to be ranked.

OpenAQ's archive, where our readings come from, has almost none for 7 of these 31 days. Cities in the United States and Europe have them from the EPA's and the European Environment Agency's own records of the same monitors; elsewhere a city's average is over its other days. Why.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

← Granite City 0% 0.75%0
Every city in Illinois, United States ranked for January 2023, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.
  1. 1Granite City
    0 of 22
  2. 2Calumet City
    0 of 31
  3. 3Franklin Park
    0 of 31
  4. 4Moline
    0 of 31
  5. 5East Saint Louis
    0 of 31
  6. 5Des Plaines
    0 of 31
  7. 7Naperville
    0 of 31
  8. 8Braidwood
    0 of 25
  9. 9Joliet
    0 of 31
  10. 9Northbrook
    0 of 31
  11. 9Rockford
    0 of 31
  12. 12Bloomington
    0 of 25
  13. 12Cary
    0 of 31
  14. 14Oak Lawn
    0 of 25
  15. 14Winthrop Harbor
    0 of 25
  16. 16Springfield
    0 of 31
  17. 17Chicago
    0 of 25
  18. 17Savoy
    0 of 25
  19. 19Jerseyville
    0 of 25
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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

All cities in the world, January 2023 · All cities in United States, January 2023 · Illinois now

Use this board

SmogRank, most polluted cities in Illinois, United States, by unhealthy days, PM2.5, January 2023, smogrank.com/us/region/illinois/history/2023-01?by=days (accessed 7 Oct 2026).

Download top 10 by average (PNG)

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.