Median AQI
35
Good
Indiana · County air quality · 2025
Posey County, Indiana
Median AQI 35 (Good). 90.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 35
- Median AQI
- 90.5%
- Good-air days
- 0
- Unhealthy days
- 81%
- Cleaner than US counties
Posey County's 2025 annual median AQI is 35 (Good), with 90.5% Good days
According to the U.S. EPA Air Quality System, Posey County, Indiana posted a 2025 median AQI of 35 (Good) across 338 monitored days, with 90.5% 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
- Posey County's 90.5% Good-day share places it cleaner than 81% of US counties in 2025.
- Closest median-AQI peer
- Atascosa County (76.0% Good, median AQI 35) is the closest nationwide median-AQI peer to Posey County.
- 2020–2025 trend
- Posey County's floor-qualifying Good-day share is worsening from 2020 to 2025 (94.6% → 90.5%).
- Median AQI
- Median AQI: 35
The verdict
According to EPA Air Quality System monitoring data, Posey County's air is good on balance, cleaner than most US counties, a median AQI of 35 with 90.5% of 338 monitored days in the Good band, driven mainly by Ozone.
- 35
- median AQI · Good
- 90.5%
- days rated Good
- Ozone
- main pollutant
- 81%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 105.
Annual release change
What changed in the 2025 EPA annual release
- Posey County's Good-day share fell from 93.2% to 90.5% between the 2024 and 2025 EPA annual releases, a change of -2.6 percentage points.
- Posey County's peak single-day AQI fell from 122 to 105 between the 2024 and 2025 EPA annual releases, a change of -17 points.
Data updated August 2026
- Good · 306 d · 90.5%
- Moderate · 31 d · 9.2%
- USG · 1 d · 0.3%
How did Posey County's air break down in 2025?
Across 338 monitored days, 306 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 105 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 338 days monitored. Median AQI: 35 (Good).
Insights: Posey County, Indiana. EPA monitors recorded a median Air Quality Index of 35 across 338 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 306 (91%) fell in the Good band (AQI 0–50), 31 (9%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 50, while the worst single-day peak hit 105 (USG). Residents averaged about 27.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (338 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -4.1 points 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 105, 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
90.5%
306 of 338 monitored days
15.5pp vs 75% target
Max AQI Recorded
105
USG
Health Grade
Excellent
90th-pct AQI 50
Posey County, Good days share 90.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Posey 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 338 monitored days across EPA AQI categories.
Good
306
91%
Moderate
31
9%
USG
1
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Posey County.
- Ozone · 338 days · 100.0%
Health Impact Assessment
Excellent
Posey County's air quality is rated Excellent based on 90.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 90.5% of monitored days in 2025, with a median AQI of 35. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 338 of 338 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Posey County. Highest Good-day share: 2022 (95.9%, 349 of 364 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 336 | 18 | 1 | 0 | 31 | 112 |
| 2021 | 344 | 16 | 0 | 0 | 32 | 77 |
| 2022 | 349 | 15 | 0 | 0 | 33 | 97 |
| 2023 | 304 | 43 | 7 | 0 | 38 | 126 |
| 2024 | 340 | 24 | 1 | 0 | 37 | 122 |
| 2025 | 306 | 31 | 1 | 0 | 35 | 105 |
How does Posey County compare?
How Posey County compares
Good-day share better than typical
Posey County 90.5%
Atascosa County, Texas 76.0%
Typical US county 76.0%
Median AQI better than typical
Posey County 35
Atascosa County, Texas 35
Typical US county 39
Unhealthy days / yr better than typical
Posey County 0
Atascosa County, Texas 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Posey County (35), not geographic neighbors.
Atascosa County, Texas
Median AQI 35 · 76.0% Good-day share
Benzie County, Michigan
Median AQI 35 · 91.1% Good-day share
Berkeley County, South Carolina
Median AQI 35 · 93.3% Good-day share
Boone County, Indiana
Median AQI 35 · 89.7% Good-day share
Brazoria County, Texas
Median AQI 35 · 80.8% Good-day share
Caroline County, Virginia
Median AQI 35 · 96.7% 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).
Aiken County, South Carolina
90.6% Good-day share · median AQI 39
Columbia County, Washington
90.4% Good-day share · median AQI 36
Smith County, Texas
90.4% Good-day share · median AQI 35
Fergus County, Montana
90.7% Good-day share · median AQI 41
Newton County, Arkansas
90.4% Good-day share · median AQI 38
Carroll County, Maryland
90.3% Good-day share · median AQI 38
Indiana counties on the map
Geographic containment only, other monitored counties in Indiana, independent of AQI or pollutant match.
What Posey 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 35 means for exposure. Health guidance
- See how Posey County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Posey County with its Indiana neighbours before drawing a conclusion about the region. All of Indiana
Based on 338 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 Posey County, Indiana? ▼
Posey County has a median Air Quality Index (AQI) of 35, rated "Good." 90.5% of monitored days (306 out of 338) had good air quality in 2025.
What is the main pollutant in Posey County? ▼
The primary pollutant in Posey County is Ozone (O3), which was the main AQI driver on 338 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Posey County have? ▼
In 2025, Posey County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 105.
Is the air quality in Posey County getting better or worse? ▼
Air quality in Posey County is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2022 at 95.9% (349 of 364 days). Lowest qualifying Good-day share: 2023 at 85.9% (304 of 354 days).
What does AQI 35 mean for health? ▼
Posey County's median AQI of 35 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Posey County compare to other counties in Indiana? ▼
Posey County has 90.5% 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 Posey County? ▼
The 90th percentile AQI for Posey County is 50, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 105 (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 Posey 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.