Median AQI
44
Good
Illinois · County air quality · 2025
Macon 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, Macon 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 PM2.5.
- 44
- median AQI · Good
- 63.7%
- days rated Good
- PM2.5
- main pollutant
- 20%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 141.
Data updated July 2026
- Good · 174 d · 63.7%
- Moderate · 96 d · 35.2%
- USG · 3 d · 1.1%
How did Macon 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 141 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 44 (Good).
Insights: Macon 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 67, while the worst single-day peak hit 141 (USG). Residents averaged about 19.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (151 days), Ozone (122 days). Across the 2020–2025 trend window, good days shifted by -40 and the median AQI moved -2 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 141, usg but never Unhealthy. Nearby counties show comparable readings: Adams (94.4% good, AQI 38); Champaign (63.7% good, AQI 44); Clark (92.1% good, AQI 36); Cook (40.5% good, AQI 53); DuPage (61.2% good, AQI 44); Effingham (95.7% good, AQI 35).
Air Quality Summary
Good Days
63.7%
174 of 273 monitored days
-11.3pp vs 75% target
Max AQI Recorded
141
USG
Health Grade
Moderate
90th-pct AQI 67
Macon County, Good days share 63.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Macon 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 Macon County.
- PM2.5 · 151 days · 55.3%
- Ozone · 122 days · 44.7%
Health Impact Assessment
Moderate
Macon 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 PM2.5, driving AQI on 151 of 273 monitored days.
5-Year Air Quality Trend
Air quality is improving in Macon County. Best year: 2024 (238 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 214 | 148 | 0 | 0 | 46 | 90 |
| 2021 | 179 | 179 | 3 | 0 | 51 | 112 |
| 2022 | 209 | 154 | 2 | 0 | 46 | 115 |
| 2023 | 171 | 178 | 14 | 1 | 51 | 287 |
| 2024 | 238 | 127 | 1 | 0 | 43 | 101 |
| 2025 | 174 | 96 | 3 | 0 | 44 | 141 |
How does Macon County compare?
How Macon County compares
Good-day share worse than US avg
Macon County 63.7%
Adams County, Illinois 94.4%
US average 76.5%
Median AQI worse than US avg
Macon County 44
Adams County, Illinois 38
US average 38
Unhealthy days / yr about average
Macon 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 Macon 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 Macon County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 44 means for exposure. Health guidance
- See how Macon County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Macon 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 Macon County, Illinois? ▼
Macon 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 Macon County? ▼
The primary pollutant in Macon County is Fine Particles (PM2.5), which was the main AQI driver on 151 days (55% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Macon County have? ▼
In 2025, Macon County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 141.
Is the air quality in Macon County getting better or worse? ▼
Air quality in Macon County is improving based on 5-year trends (2020-2025). Best year: 2024 with 238 good days. Worst year: 2023 with 171 good days.
What does AQI 44 mean for health? ▼
Macon 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 Macon County compare to other counties in Illinois? ▼
Macon County has 63.7% good air days. Nearby counties in Illinois: Adams (94.4% good), Champaign (63.7% good), Clark (92.1% good), Cook (40.5% good), DuPage (61.2% good), Effingham (95.7% good).
What is the 90th percentile AQI in Macon County? ▼
The 90th percentile AQI for Macon County is 67, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 141 (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.