Median AQI
44
Good
Illinois · County air quality · 2025
Champaign County, Illinois
Median AQI 44 (Good). 63.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 44
- Median AQI
- 63.7%
- Good-air days
- 0
- Unhealthy days
- 20%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Champaign County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 44 with 63.7% of 273 monitored days in the Good band, driven mainly by Ozone.
- 44
- median AQI · Good
- 63.7%
- days rated Good
- Ozone
- main pollutant
- 20%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 138.
Data updated July 2026
- Good · 174 d · 63.7%
- Moderate · 96 d · 35.2%
- USG · 3 d · 1.1%
How did Champaign County's air break down in 2025?
Across 273 monitored days, 174 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 138 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 44 (Good).
Insights: Champaign County, Illinois. EPA monitors recorded a median Air Quality Index of 44 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 174 (64%) fell in the Good band (AQI 0–50), 96 (35%) registered Moderate readings, and 3 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 138 (USG). Residents averaged about 19.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (153 days), PM2.5 (120 days). Across the 2020–2025 trend window, good days shifted by -76 and the median AQI moved +0 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 138, usg but never Unhealthy. Nearby counties show comparable readings: Adams (94.4% good, AQI 38); Clark (92.1% good, AQI 36); Cook (40.5% good, AQI 53); DuPage (61.2% good, AQI 44); Effingham (95.7% good, AQI 35); Hamilton (66.5% good, AQI 43).
Air Quality Summary
Good Days
63.7%
174 of 273 monitored days
-11.3pp vs 75% target
Max AQI Recorded
138
USG
Health Grade
Moderate
90th-pct AQI 64
Champaign County, Good days share 63.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Champaign County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
174
64%
Moderate
96
35%
USG
3
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Champaign County.
- Ozone · 153 days · 56.0%
- PM2.5 · 120 days · 44.0%
Health Impact Assessment
Moderate
Champaign County's air quality is rated Moderate based on 63.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 63.7% of monitored days in 2025, with a median AQI of 44. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 153 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Champaign County. Best year: 2024 (250 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 250 | 114 | 2 | 0 | 44 | 126 |
| 2021 | 236 | 129 | 0 | 0 | 44 | 99 |
| 2022 | 223 | 141 | 1 | 0 | 44 | 126 |
| 2023 | 196 | 156 | 11 | 1 | 48 | 277 |
| 2024 | 250 | 116 | 0 | 0 | 44 | 100 |
| 2025 | 174 | 96 | 3 | 0 | 44 | 138 |
How does Champaign County compare?
How Champaign County compares
Good-day share worse than US avg
Champaign County 63.7%
Adams County, Illinois 94.4%
US average 76.5%
Median AQI worse than US avg
Champaign County 44
Adams County, Illinois 38
US average 38
Unhealthy days / yr about average
Champaign County 0
Adams County, Illinois 0
US average 0
Other Counties in Illinois
Air quality comparison for nearby counties in Illinois.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Champaign County.
Baltimore County, Maryland
AQI 44 · 70.4% good
Baltimore (City) County, Maryland
AQI 44 · 68.7% good
Bartholomew County, Indiana
AQI 44 · 69.2% good
Berks County, Pennsylvania
AQI 44 · 65.6% good
Bolivar County, Mississippi
AQI 44 · 70.3% good
Brewster County, Texas
AQI 44 · 69.0% good
What Champaign County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 44 means for exposure. Health guidance
- See how Champaign County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Champaign County with its Illinois neighbours before drawing a conclusion about the region. All of Illinois
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Champaign County, Illinois? ▼
Champaign County has a median Air Quality Index (AQI) of 44, rated "Good." 63.7% of monitored days (174 out of 273) had good air quality in 2025.
What is the main pollutant in Champaign County? ▼
The primary pollutant in Champaign County is Ozone (O3), which was the main AQI driver on 153 days (56% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Champaign County have? ▼
In 2025, Champaign County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 138.
Is the air quality in Champaign County getting better or worse? ▼
Air quality in Champaign County is worsening based on 5-year trends (2020-2025). Best year: 2024 with 250 good days. Worst year: 2025 with 174 good days.
What does AQI 44 mean for health? ▼
Champaign County's median AQI of 44 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Champaign County compare to other counties in Illinois? ▼
Champaign County has 63.7% good air days. Nearby counties in Illinois: Adams (94.4% good), Clark (92.1% good), Cook (40.5% good), DuPage (61.2% good), Effingham (95.7% good), Hamilton (66.5% good).
What is the 90th percentile AQI in Champaign County? ▼
The 90th percentile AQI for Champaign County is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 138 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.