Median AQI
43
Good
Ohio · County air quality · 2025
Madison County, Ohio
Median AQI 43 (Good). 77.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 77.5%
- Good-air days
- 0
- Unhealthy days
- 45%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Madison County's air is good on balance, more polluted than the median US county, a median AQI of 43 with 77.5% of 213 monitored days in the Good band, driven mainly by Ozone.
- 43
- median AQI · Good
- 77.5%
- days rated Good
- Ozone
- main pollutant
- 45%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 112.
Data updated July 2026
- Good · 165 d · 77.5%
- Moderate · 43 d · 20.2%
- USG · 5 d · 2.3%
How did Madison County's air break down in 2025?
Across 213 monitored days, 165 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 112 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 213 days monitored. Median AQI: 43 (Good).
Insights: Madison County, Ohio. EPA monitors recorded a median Air Quality Index of 43 across 213 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 165 (77%) fell in the Good band (AQI 0–50), 43 (20%) registered Moderate readings, and 5 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 71, while the worst single-day peak hit 112 (USG). Residents averaged about 23.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (213 days). Across the 2020–2025 trend window, good days shifted by -55 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 112, usg but never Unhealthy. Nearby counties show comparable readings: Allen (65.9% good, AQI 43); Ashtabula (81.2% good, AQI 43); Athens (80.3% good, AQI 33); Belmont (63.0% good, AQI 42); Butler (33.3% good, AQI 55); Clark (59.4% good, AQI 46).
Air Quality Summary
Good Days
77.5%
165 of 213 monitored days
2.5pp vs 75% target
Max AQI Recorded
112
USG
Health Grade
Good
90th-pct AQI 71
Madison County, Good days share 77.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Madison 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 213 monitored days across EPA AQI categories.
Good
165
77%
Moderate
43
20%
USG
5
2%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Madison County.
- Ozone · 213 days · 100.0%
Health Impact Assessment
Good
Madison County's air quality is rated Good based on 77.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 77.5% of monitored days in 2025, with a median AQI of 43. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 213 of 213 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Madison County. Best year: 2020 (220 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 220 | 25 | 0 | 0 | 39 | 84 |
| 2021 | 212 | 17 | 0 | 0 | 39 | 84 |
| 2022 | 218 | 26 | 0 | 0 | 39 | 90 |
| 2023 | 197 | 44 | 2 | 0 | 44 | 105 |
| 2024 | 203 | 42 | 0 | 0 | 44 | 100 |
| 2025 | 165 | 43 | 5 | 0 | 43 | 112 |
How does Madison County compare?
How Madison County compares
Good-day share better than US avg
Madison County 77.5%
Allen County, Ohio 65.9%
US average 76.5%
Median AQI worse than US avg
Madison County 43
Allen County, Ohio 43
US average 38
Unhealthy days / yr about average
Madison County 0
Allen County, Ohio 0
US average 0
Other Counties in Ohio
Air quality comparison for nearby counties in Ohio.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Madison County.
Allegan County, Michigan
AQI 43 · 71.2% good
Allen County, Ohio
AQI 43 · 65.9% good
Ashtabula County, Ohio
AQI 43 · 81.2% good
Bell County, Kentucky
AQI 43 · 63.5% good
Boise County, Idaho
AQI 43 · 72.9% good
Brazos County, Texas
AQI 43 · 63.4% good
What Madison 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 43 means for exposure. Health guidance
- See how Madison County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Madison County with its Ohio neighbours before drawing a conclusion about the region. All of Ohio
Based on 213 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 Madison County, Ohio? ▼
Madison County has a median Air Quality Index (AQI) of 43, rated "Good." 77.5% of monitored days (165 out of 213) had good air quality in 2025.
What is the main pollutant in Madison County? ▼
The primary pollutant in Madison County is Ozone (O3), which was the main AQI driver on 213 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Madison County have? ▼
In 2025, Madison County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 112.
Is the air quality in Madison County getting better or worse? ▼
Air quality in Madison County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 220 good days. Worst year: 2025 with 165 good days.
What does AQI 43 mean for health? ▼
Madison County's median AQI of 43 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 Madison County compare to other counties in Ohio? ▼
Madison County has 77.5% good air days. Nearby counties in Ohio: Allen (65.9% good), Ashtabula (81.2% good), Athens (80.3% good), Belmont (63.0% good), Butler (33.3% good), Clark (59.4% good).
What is the 90th percentile AQI in Madison County? ▼
The 90th percentile AQI for Madison County is 71, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 112 (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.