SmogRank / World / United States / Illinois / February 2023

Most unhealthy days in Illinois, United States, February 2023

12 cities in Illinois, United States ranked by their share of unhealthy days over the 28 days. The most unhealthy days: Calumet City, United States, 0 of 28 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 25 of these 28 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; many cities elsewhere are missing from this board, not clean. 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.

← Calumet City 0% 0.75%0
Every city in Illinois, United States ranked for February 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. 1Calumet City
    0 of 28
  2. 2East Saint Louis
    0 of 28
  3. 3Franklin Park
    0 of 28
  4. 4Naperville
    0 of 28
  5. 5Joliet
    0 of 28
  6. 6Decatur
    0 of 25
  7. 6Moline
    0 of 28
  8. 6Rockford
    0 of 28
  9. 9Cary
    0 of 28
  10. 9Des Plaines
    0 of 28
  11. 9Northbrook
    0 of 28
  12. 12Springfield
    0 of 28
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, February 2023 · All cities in United States, February 2023 · Illinois now

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SmogRank, most polluted cities in Illinois, United States, by unhealthy days, PM2.5, February 2023, smogrank.com/us/region/illinois/history/2023-02?by=days (accessed 7 Oct 2026).

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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.