Median AQI
42
Good
Iowa · County air quality · 2025
Palo Alto County, Iowa
Median AQI 42 (Good). 69.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 42
- Median AQI
- 69.4%
- Good-air days
- 0
- Unhealthy days
- 30%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Palo Alto County's air is good on balance, more polluted than the median US county, a median AQI of 42 with 69.4% of 304 monitored days in the Good band, driven mainly by PM2.5.
- 42
- median AQI · Good
- 69.4%
- days rated Good
- PM2.5
- main pollutant
- 30%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 134.
Data updated July 2026
- Good · 211 d · 69.4%
- Moderate · 84 d · 27.6%
- USG · 9 d · 3.0%
How did Palo Alto County's air break down in 2025?
Across 304 monitored days, 211 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 134 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 304 days monitored. Median AQI: 42 (Good).
Insights: Palo Alto County, Iowa. EPA monitors recorded a median Air Quality Index of 42 across 304 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 211 (69%) fell in the Good band (AQI 0–50), 84 (28%) registered Moderate readings, and 9 (3%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 74, while the worst single-day peak hit 134 (USG). Residents averaged about 20.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (155 days), Ozone (149 days). Across the 2020–2025 trend window, good days shifted by -62 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 134, 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); Harrison (83.0% good, AQI 39); Johnson (71.0% good, AQI 36); Linn (61.2% good, AQI 44).
Air Quality Summary
Good Days
69.4%
211 of 304 monitored days
-5.6pp vs 75% target
Max AQI Recorded
134
USG
Health Grade
Moderate
90th-pct AQI 74
Palo Alto County, Good days share 69.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
Palo Alto 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 304 monitored days across EPA AQI categories.
Good
211
69%
Moderate
84
28%
USG
9
3%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Palo Alto County.
- PM2.5 · 155 days · 51.0%
- Ozone · 149 days · 49.0%
Health Impact Assessment
Moderate
Palo Alto County's air quality is rated Moderate based on 69.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 69.4% of monitored days in 2025, with a median AQI of 42. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 155 of 304 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Palo Alto County. Best year: 2020 (273 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 273 | 93 | 0 | 0 | 40 | 87 |
| 2021 | 250 | 108 | 2 | 2 | 43 | 167 |
| 2022 | 271 | 94 | 0 | 0 | 42 | 79 |
| 2023 | 211 | 135 | 14 | 4 | 46 | 161 |
| 2024 | 268 | 95 | 0 | 0 | 42 | 96 |
| 2025 | 211 | 84 | 9 | 0 | 42 | 134 |
How does Palo Alto County compare?
How Palo Alto County compares
Good-day share worse than US avg
Palo Alto County 69.4%
Black Hawk County, Iowa 56.6%
US average 76.5%
Median AQI worse than US avg
Palo Alto County 42
Black Hawk County, Iowa 48
US average 38
Unhealthy days / yr about average
Palo Alto 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 Palo Alto County.
Adams County, Pennsylvania
AQI 42 · 73.8% good
Anderson County, Tennessee
AQI 42 · 91.0% good
Andrew County, Missouri
AQI 42 · 84.3% good
Armstrong County, Pennsylvania
AQI 42 · 68.1% good
Baldwin County, Alabama
AQI 42 · 72.2% good
Belmont County, Ohio
AQI 42 · 63.0% good
What Palo Alto 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 42 means for exposure. Health guidance
- See how Palo Alto County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Palo Alto County with its Iowa neighbours before drawing a conclusion about the region. All of Iowa
Based on 304 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 Palo Alto County, Iowa? ▼
Palo Alto County has a median Air Quality Index (AQI) of 42, rated "Good." 69.4% of monitored days (211 out of 304) had good air quality in 2025.
What is the main pollutant in Palo Alto County? ▼
The primary pollutant in Palo Alto County is Fine Particles (PM2.5), which was the main AQI driver on 155 days (51% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Palo Alto County have? ▼
In 2025, Palo Alto County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 134.
Is the air quality in Palo Alto County getting better or worse? ▼
Air quality in Palo Alto County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 273 good days. Worst year: 2025 with 211 good days.
What does AQI 42 mean for health? ▼
Palo Alto County's median AQI of 42 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 Palo Alto County compare to other counties in Iowa? ▼
Palo Alto County has 69.4% good air days. Nearby counties in Iowa: Black Hawk (56.6% good), Bremer (87.1% good), Clinton (59.9% good), Harrison (83.0% good), Johnson (71.0% good), Linn (61.2% good).
What is the 90th percentile AQI in Palo Alto County? ▼
The 90th percentile AQI for Palo Alto County is 74, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 134 (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.