Median AQI
41
Good
Indiana · County air quality · 2025
Madison County, Indiana
Median AQI 41 (Good). 71.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 41
- Median AQI
- 71.2%
- Good-air days
- 0
- Unhealthy days
- 35%
- Cleaner than US counties
Madison County's 2025 annual median AQI is 41 (Good), with 71.2% Good days
According to the U.S. EPA Air Quality System, Madison County, Indiana posted a 2025 median AQI of 41 (Good) across 365 monitored days, with 71.2% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Madison County's 71.2% Good-day share places it cleaner than 35% of US counties in 2025.
- Closest median-AQI peer
- Armstrong County (70.5% Good, median AQI 41) is the closest nationwide median-AQI peer to Madison County.
- 2020–2025 trend
- Madison County's floor-qualifying Good-day share is improving from 2020 to 2025 (63.7% → 71.2%).
- Median AQI
- Median AQI: 41
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 41 with 71.2% of 365 monitored days in the Good band, driven mainly by Ozone.
- 41
- median AQI · Good
- 71.2%
- days rated Good
- Ozone
- main pollutant
- 35%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 122.
Annual release change
What changed in the 2025 EPA annual release
- Madison County's peak single-day AQI rose from 97 to 122 between the 2024 and 2025 EPA annual releases, a change of +25 points.
Data updated August 2026
- Good · 260 d · 71.2%
- Moderate · 103 d · 28.2%
- USG · 2 d · 0.5%
How did Madison County's air break down in 2025?
Across 365 monitored days, 260 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 122 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 41 (Good).
Insights: Madison County, Indiana. EPA monitors recorded a median Air Quality Index of 41 across 365 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 260 (71%) fell in the Good band (AQI 0–50), 103 (28%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 61, while the worst single-day peak hit 122 (USG). Residents averaged about 21.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (192 days), PM2.5 (173 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +7.6 points and the median AQI moved -3 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 122, usg but never Unhealthy. Nearby counties show comparable readings: Allen (60.0% good, AQI 44); Bartholomew (72.6% good, AQI 43); Boone (89.7% good, AQI 35); Brown (95.9% good, AQI 34); Carroll (90.8% good, AQI 35); Clark (58.1% good, AQI 46).
Air Quality Summary
Good Days
71.2%
260 of 365 monitored days
-3.8pp vs 75% target
Max AQI Recorded
122
USG
Health Grade
Moderate
90th-pct AQI 61
Madison County, Good days share 71.2%
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 365 monitored days across EPA AQI categories.
Good
260
71%
Moderate
103
28%
USG
2
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 Madison County.
- Ozone · 192 days · 52.6%
- PM2.5 · 173 days · 47.4%
Health Impact Assessment
Moderate
Madison County's air quality is rated Moderate based on 71.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 71.2% of monitored days in 2025, with a median AQI of 41. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 192 of 365 monitored days.
5-Year Air Quality Trend
Air quality is improving in Madison County. Highest Good-day share: 2024 (72.1%, 263 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 233 | 133 | 0 | 0 | 44 | 97 |
| 2021 | 199 | 165 | 0 | 0 | 48 | 97 |
| 2022 | 224 | 137 | 4 | 0 | 45 | 133 |
| 2023 | 203 | 150 | 10 | 1 | 48 | 229 |
| 2024 | 263 | 102 | 0 | 0 | 42 | 97 |
| 2025 | 260 | 103 | 2 | 0 | 41 | 122 |
How does Madison County compare?
How Madison County compares
Good-day share worse than typical
Madison County 71.2%
Armstrong County, Pennsylvania 70.5%
Typical US county 76.0%
Median AQI worse than typical
Madison County 41
Armstrong County, Pennsylvania 41
Typical US county 39
Unhealthy days / yr better than typical
Madison County 0
Armstrong County, Pennsylvania 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Madison County (41), not geographic neighbors.
Armstrong County, Pennsylvania
Median AQI 41 · 70.5% Good-day share
Benewah County, Idaho
Median AQI 41 · 63.4% Good-day share
Berrien County, Michigan
Median AQI 41 · 80.9% Good-day share
Callaway County, Missouri
Median AQI 41 · 89.6% Good-day share
Cambria County, Pennsylvania
Median AQI 41 · 74.5% Good-day share
Cass County, Missouri
Median AQI 41 · 77.6% Good-day share
Same primary pollutant: Ozone
Ozone led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Chester County, Pennsylvania
71.3% Good-day share · median AQI 43
Bergen County, New Jersey
71.1% Good-day share · median AQI 40
Douglas County, Nebraska
71.0% Good-day share · median AQI 42
Blount County, Tennessee
71.5% Good-day share · median AQI 44
Lewis and Clark County, Montana
71.5% Good-day share · median AQI 44
Catron County, New Mexico
71.7% Good-day share · median AQI 45
Indiana counties on the map
Geographic containment only, other monitored counties in Indiana, independent of AQI or pollutant match.
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 41 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 Indiana neighbours before drawing a conclusion about the region. All of Indiana
Based on 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Madison County, Indiana? ▼
Madison County has a median Air Quality Index (AQI) of 41, rated "Good." 71.2% of monitored days (260 out of 365) 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 192 days (53% 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 122.
Is the air quality in Madison County getting better or worse? ▼
Air quality in Madison County is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2024 at 72.1% (263 of 365 days). Lowest qualifying Good-day share: 2021 at 54.7% (199 of 364 days).
What does AQI 41 mean for health? ▼
Madison County's median AQI of 41 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Madison County compare to other counties in Indiana? ▼
Madison County has 71.2% good air days. Nearby counties in Indiana: Allen (60.0% good), Bartholomew (72.6% good), Boone (89.7% good), Brown (95.9% good), Carroll (90.8% good), Clark (58.1% good).
What is the 90th percentile AQI in Madison County? ▼
The 90th percentile AQI for Madison County is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 122 (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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Madison County, Indiana · 2020–2025
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Every figure on PlainAirData 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.