DataOfWorld

Air quality reference

Chicago-Naperville-Elgin, IL-IN-WI

Chicago-Naperville-Elgin, IL-IN-WI has a published AQI value of 3, categorized as Good, for 2026-05-01T00:00:00+00:00. The defining parameter is CO, based on 2 monitoring sites. AQI is a communication index rather than a direct pollutant concentration, and values from different dates, averaging periods or providers should not be treated as interchangeable. This profile provides measurement context and same-category links but does not provide individualized medical advice.

1,149National Rank
1,261National Count
3.0AQI
9.0National Percentile
1,042Category Observations
1Country Count
5Category Peers Count

Key facts

Location
Chicago-Naperville-Elgin, IL-IN-WI
Air quality index
3
Category
Good
Defining parameter
CO
Sites reporting
2
Measured at
2026-05-01T00:00:00+00:00
Measurement context
Daily AQI summary from U.S. EPA AirData; values are not direct pollutant concentrations

Historical air-quality context

Published EPA annual CBSA indicators

Annual AQI summaries are shown independently from pollutant concentrations. Current-year values are provisional because reporting is incomplete and can be revised.

Annual indicator

Days with published AQI

121.00 days2026

EPA annual CBSA summary field: Days with AQI. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
2026121.00 daysprovisional-current-year—
2025365.00 days——
2024366.00 days——
2023365.00 days——
2022365.00 days——
2021365.00 days——
2020366.00 days——
2019365.00 days——
2018365.00 days——
2017365.00 days——
2016366.00 days——
2015365.00 days——
2014365.00 days——
2013365.00 days——
2012366.00 days——
2011365.00 days——
2010365.00 days——
2009365.00 days——
2008366.00 days——
2007365.00 days——
2006365.00 days——
2005365.00 days——
2004366.00 days——
2003365.00 days——
2002365.00 days——
2001365.00 days——
2000366.00 days——
1999365.00 days——
1998365.00 days——
1997365.00 days——
1996366.00 days——
1995365.00 days——
1994365.00 days——
1993365.00 days——
1992366.00 days——
1991365.00 days——
1990365.00 days——
1989365.00 days——
1988366.00 days——
1987365.00 days——
1986365.00 days——
1985365.00 days——
1984366.00 days——
1983365.00 days——
1982365.00 days——
1981365.00 days——
1980366.00 days——

Annual indicator

Good AQI days

46.00 days2026

EPA annual CBSA summary field: Good Days. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
202646.00 daysprovisional-current-year—
2025109.00 days——
202495.00 days——
202376.00 days——
202293.00 days——
202167.00 days——
202062.00 days——
201953.00 days——
201853.00 days——
201782.00 days——
201679.00 days——
201539.00 days——
201422.00 days——
201335.00 days——
201221.00 days——
201120.00 days——
201018.00 days——
200921.00 days——
200815.00 days——
200711.00 days——
200624.00 days——
200525.00 days——
200421.00 days——
200324.00 days——
200212.00 days——
200115.00 days——
200015.00 days——
199922.00 days——
199880.00 days——
1997129.00 days——
1996131.00 days——
1995131.00 days——
1994129.00 days——
1993156.00 days——
1992163.00 days——
1991142.00 days——
1990108.00 days——
198977.00 days——
1988101.00 days——
198777.00 days——
198621.00 days——
198553.00 days——
198470.00 days——
198386.00 days——
198279.00 days——
198184.00 days——
198030.00 days——

Annual indicator

Hazardous AQI days

0.00 days2026

EPA annual CBSA summary field: Hazardous Days. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
20260.00 daysprovisional-current-year—
20250.00 days——
20240.00 days——
20230.00 days——
20220.00 days——
20210.00 days——
20200.00 days——
20190.00 days——
20180.00 days——
20170.00 days——
20160.00 days——
20150.00 days——
20140.00 days——
20130.00 days——
20120.00 days——
20110.00 days——
20100.00 days——
20090.00 days——
20080.00 days——
20070.00 days——
20060.00 days——
20050.00 days——
20040.00 days——
20030.00 days——
20020.00 days——
20010.00 days——
20000.00 days——
19990.00 days——
19980.00 days——
19970.00 days——
19961.00 days——
19950.00 days——
19940.00 days——
19930.00 days——
19920.00 days——
19910.00 days——
19900.00 days——
19890.00 days——
19880.00 days——
19870.00 days——
19860.00 days——
19850.00 days——
19840.00 days——
19830.00 days——
19820.00 days——
19810.00 days——
19800.00 days——

Annual indicator

Maximum daily AQI

99.00 AQI index2026

EPA annual CBSA summary field: Max AQI. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PeriodAQI indexSource flagConfidentiality
202699.00 AQI indexprovisional-current-year—
2025219.00 AQI index——
2024166.00 AQI index——
2023246.00 AQI index——
2022202.00 AQI index——
2021175.00 AQI index——
2020197.00 AQI index——
2019174.00 AQI index——
2018177.00 AQI index——
2017177.00 AQI index——
2016242.00 AQI index——
2015195.00 AQI index——
2014156.00 AQI index——
2013198.00 AQI index——
2012206.00 AQI index——
2011177.00 AQI index——
2010159.00 AQI index——
2009202.00 AQI index——
2008140.00 AQI index——
2007203.00 AQI index——
2006164.00 AQI index——
2005208.00 AQI index——
2004179.00 AQI index——
2003190.00 AQI index——
2002223.00 AQI index——
2001209.00 AQI index——
2000190.00 AQI index——
1999202.00 AQI index——
1998217.00 AQI index——
1997216.00 AQI index——
1996504.00 AQI index——
1995225.00 AQI index——
1994240.00 AQI index——
1993203.00 AQI index——
1992237.00 AQI index——
1991224.00 AQI index——
1990218.00 AQI index——
1989227.00 AQI index——
1988285.00 AQI index——
1987261.00 AQI index——
1986205.00 AQI index——
1985215.00 AQI index——
1984234.00 AQI index——
1983242.00 AQI index——
1982218.00 AQI index——
1981236.00 AQI index——
1980249.00 AQI index——

Annual indicator

Median daily AQI

54.00 AQI index2026

EPA annual CBSA summary field: Median AQI. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PeriodAQI indexSource flagConfidentiality
202654.00 AQI indexprovisional-current-year—
202556.00 AQI index——
202456.00 AQI index——
202360.00 AQI index——
202256.00 AQI index——
202161.00 AQI index——
202060.00 AQI index——
201960.00 AQI index——
201861.00 AQI index——
201757.00 AQI index——
201658.00 AQI index——
201561.00 AQI index——
201466.00 AQI index——
201362.00 AQI index——
201266.00 AQI index——
201166.00 AQI index——
201071.00 AQI index——
200965.00 AQI index——
200873.00 AQI index——
200776.00 AQI index——
200669.00 AQI index——
200574.00 AQI index——
200471.00 AQI index——
200370.00 AQI index——
200274.00 AQI index——
200177.00 AQI index——
200077.00 AQI index——
199974.00 AQI index——
199868.00 AQI index——
199757.00 AQI index——
199656.00 AQI index——
199557.00 AQI index——
199457.00 AQI index——
199354.00 AQI index——
199252.00 AQI index——
199156.00 AQI index——
199064.00 AQI index——
198968.00 AQI index——
198867.00 AQI index——
198767.00 AQI index——
198682.00 AQI index——
198567.00 AQI index——
198467.00 AQI index——
198369.00 AQI index——
198271.00 AQI index——
198166.00 AQI index——
198080.00 AQI index——

Annual indicator

Moderate AQI days

75.00 days2026

EPA annual CBSA summary field: Moderate Days. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
202675.00 daysprovisional-current-year—
2025224.00 days——
2024254.00 days——
2023246.00 days——
2022257.00 days——
2021270.00 days——
2020280.00 days——
2019299.00 days——
2018286.00 days——
2017258.00 days——
2016259.00 days——
2015312.00 days——
2014325.00 days——
2013313.00 days——
2012295.00 days——
2011321.00 days——
2010312.00 days——
2009322.00 days——
2008306.00 days——
2007296.00 days——
2006317.00 days——
2005266.00 days——
2004304.00 days——
2003283.00 days——
2002287.00 days——
2001261.00 days——
2000289.00 days——
1999266.00 days——
1998222.00 days——
1997200.00 days——
1996192.00 days——
1995174.00 days——
1994190.00 days——
1993178.00 days——
1992169.00 days——
1991147.00 days——
1990168.00 days——
1989204.00 days——
1988157.00 days——
1987220.00 days——
1986248.00 days——
1985253.00 days——
1984221.00 days——
1983184.00 days——
1982208.00 days——
1981213.00 days——
1980229.00 days——

Annual indicator

90th percentile daily AQI

74.00 AQI index2026

EPA annual CBSA summary field: 90th Percentile AQI. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PeriodAQI indexSource flagConfidentiality
202674.00 AQI indexprovisional-current-year—
202597.00 AQI index——
202487.00 AQI index——
2023105.00 AQI index——
202284.00 AQI index——
202197.00 AQI index——
202090.00 AQI index——
201980.00 AQI index——
201890.00 AQI index——
201790.00 AQI index——
201688.00 AQI index——
201585.00 AQI index——
201488.00 AQI index——
201384.00 AQI index——
2012115.00 AQI index——
201193.00 AQI index——
2010100.00 AQI index——
200992.00 AQI index——
2008102.00 AQI index——
2007112.00 AQI index——
200693.00 AQI index——
2005126.00 AQI index——
2004105.00 AQI index——
2003112.00 AQI index——
2002126.00 AQI index——
2001136.00 AQI index——
2000113.00 AQI index——
1999133.00 AQI index——
1998119.00 AQI index——
1997100.00 AQI index——
1996105.00 AQI index——
1995129.00 AQI index——
1994105.00 AQI index——
199393.00 AQI index——
1992100.00 AQI index——
1991156.00 AQI index——
1990140.00 AQI index——
1989136.00 AQI index——
1988174.00 AQI index——
1987133.00 AQI index——
1986108.00 AQI index——
1985112.00 AQI index——
1984136.00 AQI index——
1983164.00 AQI index——
1982126.00 AQI index——
1981120.00 AQI index——
1980153.00 AQI index——

Annual indicator

Unhealthy AQI days

0.00 days2026

EPA annual CBSA summary field: Unhealthy Days. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
20260.00 daysprovisional-current-year—
20255.00 days——
20242.00 days——
20238.00 days——
20222.00 days——
20212.00 days——
20205.00 days——
20191.00 days——
20186.00 days——
20172.00 days——
20164.00 days——
20153.00 days——
20141.00 days——
20131.00 days——
201210.00 days——
20119.00 days——
20102.00 days——
20091.00 days——
20080.00 days——
20079.00 days——
20064.00 days——
200523.00 days——
20046.00 days——
200312.00 days——
200220.00 days——
200128.00 days——
200010.00 days——
199919.00 days——
199813.00 days——
199712.00 days——
19966.00 days——
199516.00 days——
19949.00 days——
19934.00 days——
19926.00 days——
199130.00 days——
199026.00 days——
198926.00 days——
198826.00 days——
198716.00 days——
19868.00 days——
19859.00 days——
198421.00 days——
198332.00 days——
198217.00 days——
198112.00 days——
198033.00 days——

Annual indicator

Unhealthy for sensitive groups days

0.00 days2026

EPA annual CBSA summary field: Unhealthy for Sensitive Groups Days. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
20260.00 daysprovisional-current-year—
202526.00 days——
202415.00 days——
202333.00 days——
202212.00 days——
202126.00 days——
202019.00 days——
201912.00 days——
201820.00 days——
201723.00 days——
201623.00 days——
201511.00 days——
201417.00 days——
201316.00 days——
201239.00 days——
201115.00 days——
201033.00 days——
200920.00 days——
200845.00 days——
200748.00 days——
200620.00 days——
200549.00 days——
200435.00 days——
200346.00 days——
200238.00 days——
200160.00 days——
200052.00 days——
199957.00 days——
199846.00 days——
199722.00 days——
199632.00 days——
199533.00 days——
199433.00 days——
199326.00 days——
199224.00 days——
199136.00 days——
199061.00 days——
198954.00 days——
198857.00 days——
198743.00 days——
198687.00 days——
198545.00 days——
198444.00 days——
198347.00 days——
198256.00 days——
198149.00 days——
198067.00 days——

Annual indicator

Very unhealthy AQI days

0.00 days2026

EPA annual CBSA summary field: Very Unhealthy Days. Current-year values are provisional because reporting is incomplete and can be revised. Values retain the source period and unit.

View source data
PerioddaysSource flagConfidentiality
20260.00 daysprovisional-current-year—
20251.00 days——
20240.00 days——
20232.00 days——
20221.00 days——
20210.00 days——
20200.00 days——
20190.00 days——
20180.00 days——
20170.00 days——
20161.00 days——
20150.00 days——
20140.00 days——
20130.00 days——
20121.00 days——
20110.00 days——
20100.00 days——
20091.00 days——
20080.00 days——
20071.00 days——
20060.00 days——
20052.00 days——
20040.00 days——
20030.00 days——
20028.00 days——
20011.00 days——
20000.00 days——
19991.00 days——
19984.00 days——
19972.00 days——
19964.00 days——
199511.00 days——
19944.00 days——
19931.00 days——
19924.00 days——
199110.00 days——
19902.00 days——
19894.00 days——
198825.00 days——
19879.00 days——
19861.00 days——
19855.00 days——
198410.00 days——
198316.00 days——
19825.00 days——
19817.00 days——
19807.00 days——

Explore connected data

Country context

Open the country profile for broader geographic and economic context.

United States

Explore connected data

Locations with the same AQI category

Other EPA observations sharing this reported category.

Aberdeen, SDAberdeen, WAAlbany, GAAlbany-Schenectady-Troy, NYAlbuquerque, NM

Field-level provenance

Sources for this profile

Dates and licenses apply to the specific facts and series supplied by each source.

Reference data can change. Verify consequential decisions against the original source.