Median AQI
39
Good
Iowa · County air quality · 2025
Harrison County, Iowa
Median AQI 39 (Good). 83.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 83.0%
- Good-air days
- 0
- Unhealthy days
- 60%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Harrison County's air is good on balance, cleaner than the median US county, a median AQI of 39 with 83.0% of 236 monitored days in the Good band, driven mainly by Ozone.
- 39
- median AQI · Good
- 83.0%
- days rated Good
- Ozone
- main pollutant
- 60%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 119.
Data updated July 2026
- Good · 196 d · 83.1%
- Moderate · 38 d · 16.1%
- USG · 2 d · 0.8%
How did Harrison County's air break down in 2025?
Across 236 monitored days, 196 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 119 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 236 days monitored. Median AQI: 39 (Good).
Insights: Harrison County, Iowa. EPA monitors recorded a median Air Quality Index of 39 across 236 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 196 (83%) fell in the Good band (AQI 0–50), 38 (16%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 64, while the worst single-day peak hit 119 (USG). Residents averaged about 24.9 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (236 days). Across the 2020–2025 trend window, good days shifted by -27 and the median AQI moved +2 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 119, usg but never Unhealthy. Nearby counties show comparable readings: Black Hawk (56.6% good, AQI 48); Bremer (87.1% good, AQI 38); Clinton (59.9% good, AQI 45); Johnson (71.0% good, AQI 36); Linn (61.2% good, AQI 44); Montgomery (68.8% good, AQI 43).
Air Quality Summary
Good Days
83.0%
196 of 236 monitored days
8.0pp vs 75% target
Max AQI Recorded
119
USG
Health Grade
Good
90th-pct AQI 64
Harrison County, Good days share 83.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Harrison 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 236 monitored days across EPA AQI categories.
Good
196
83%
Moderate
38
16%
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 Harrison County.
- Ozone · 236 days · 100.0%
Health Impact Assessment
Good
Harrison County's air quality is rated Good based on 83.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 83.0% of monitored days in 2025, with a median AQI of 39. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 236 of 236 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Harrison County. Best year: 2020 (223 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 223 | 19 | 0 | 0 | 37 | 87 |
| 2021 | 216 | 27 | 0 | 0 | 39 | 87 |
| 2022 | 210 | 27 | 0 | 0 | 40 | 84 |
| 2023 | 163 | 59 | 16 | 0 | 44 | 140 |
| 2024 | 208 | 36 | 0 | 0 | 42 | 90 |
| 2025 | 196 | 38 | 2 | 0 | 39 | 119 |
How does Harrison County compare?
How Harrison County compares
Good-day share better than US avg
Harrison County 83.0%
Black Hawk County, Iowa 56.6%
US average 76.5%
Median AQI worse than US avg
Harrison County 39
Black Hawk County, Iowa 48
US average 38
Unhealthy days / yr about average
Harrison County 0
Black Hawk County, Iowa 1
US average 0
Other Counties in Iowa
Air quality comparison for nearby counties in Iowa.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Harrison County.
Ada County, Idaho
AQI 39 · 80.6% good
Aiken County, South Carolina
AQI 39 · 89.1% good
Albany County, New York
AQI 39 · 67.4% good
Alexander County, North Carolina
AQI 39 · 92.4% good
Ashland County, Wisconsin
AQI 39 · 85.6% good
Bennington County, Vermont
AQI 39 · 82.9% good
What Harrison 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 39 means for exposure. Health guidance
- See how Harrison County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Harrison County with its Iowa neighbours before drawing a conclusion about the region. All of Iowa
Based on 236 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 Harrison County, Iowa? ▼
Harrison County has a median Air Quality Index (AQI) of 39, rated "Good." 83.0% of monitored days (196 out of 236) had good air quality in 2025.
What is the main pollutant in Harrison County? ▼
The primary pollutant in Harrison County is Ozone (O3), which was the main AQI driver on 236 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Harrison County have? ▼
In 2025, Harrison County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 119.
Is the air quality in Harrison County getting better or worse? ▼
Air quality in Harrison County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 223 good days. Worst year: 2023 with 163 good days.
What does AQI 39 mean for health? ▼
Harrison County's median AQI of 39 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 Harrison County compare to other counties in Iowa? ▼
Harrison County has 83.0% good air days. Nearby counties in Iowa: Black Hawk (56.6% good), Bremer (87.1% good), Clinton (59.9% good), Johnson (71.0% good), Linn (61.2% good), Montgomery (68.8% good).
What is the 90th percentile AQI in Harrison County? ▼
The 90th percentile AQI for Harrison County is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 119 (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.