Median AQI
43
Good
Iowa · County air quality · 2025
Montgomery County, Iowa
Median AQI 43 (Good). 69.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 43
- Median AQI
- 69.3%
- Good-air days
- 0
- Unhealthy days
- 31%
- Cleaner than US counties
Montgomery County's 2025 annual median AQI is 43 (Good), with 69.3% Good days
According to the U.S. EPA Air Quality System, Montgomery County, Iowa posted a 2025 median AQI of 43 (Good) across 365 monitored days, with 69.3% 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
- Montgomery County's 69.3% Good-day share places it cleaner than 31% of US counties in 2025.
- Closest median-AQI peer
- Ashtabula County (81.2% Good, median AQI 43) is the closest nationwide median-AQI peer to Montgomery County.
- 2020–2025 trend
- Montgomery County's floor-qualifying Good-day share is worsening from 2020 to 2025 (75.7% → 69.3%).
- Median AQI
- Median AQI: 43
The verdict
According to EPA Air Quality System monitoring data, Montgomery County's air is good on balance, more polluted than the median US county, a median AQI of 43 with 69.3% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 43
- median AQI · Good
- 69.3%
- days rated Good
- PM2.5
- main pollutant
- 31%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 133.
Annual release change
What changed in the 2025 EPA annual release
- Montgomery County's Good-day share fell from 76.8% to 69.3% between the 2024 and 2025 EPA annual releases, a change of -7.5 percentage points.
- Montgomery County's peak single-day AQI rose from 80 to 133 between the 2024 and 2025 EPA annual releases, a change of +53 points.
Data updated August 2026
- Good · 253 d · 69.3%
- Moderate · 111 d · 30.4%
- USG · 1 d · 0.3%
How did Montgomery County's air break down in 2025?
Across 365 monitored days, 253 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 133 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 43 (Good).
Insights: Montgomery County, Iowa. EPA monitors recorded a median Air Quality Index of 43 across 365 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 253 (69%) fell in the Good band (AQI 0–50), 111 (30%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 61, while the worst single-day peak hit 133 (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 (233 days), Ozone (132 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -6.4 points 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 133, usg but never Unhealthy. Nearby counties show comparable readings: Black Hawk (53.4% good, AQI 49); Bremer (87.1% good, AQI 38); Clinton (59.5% good, AQI 45); Harrison (83.0% good, AQI 39); Johnson (70.1% good, AQI 37); Linn (61.4% good, AQI 44).
Air Quality Summary
Good Days
69.3%
253 of 365 monitored days
-5.7pp vs 75% target
Max AQI Recorded
133
USG
Health Grade
Moderate
90th-pct AQI 61
Montgomery County, Good days share 69.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Montgomery 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
253
69%
Moderate
111
30%
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 Montgomery County.
- PM2.5 · 233 days · 63.8%
- Ozone · 132 days · 36.2%
Health Impact Assessment
Moderate
Montgomery County's air quality is rated Moderate based on 69.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 69.3% 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 PM2.5, driving AQI on 233 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Montgomery County. Highest Good-day share: 2022 (84.0%, 305 of 363 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 277 | 89 | 0 | 0 | 41 | 79 |
| 2021 | 250 | 100 | 1 | 0 | 42 | 112 |
| 2022 | 305 | 58 | 0 | 0 | 39 | 79 |
| 2023 | 226 | 131 | 7 | 0 | 44 | 147 |
| 2024 | 272 | 82 | 0 | 0 | 42 | 80 |
| 2025 | 253 | 111 | 1 | 0 | 43 | 133 |
How does Montgomery County compare?
How Montgomery County compares
Good-day share worse than typical
Montgomery County 69.3%
Ashtabula County, Ohio 81.2%
Typical US county 76.0%
Median AQI worse than typical
Montgomery County 43
Ashtabula County, Ohio 43
Typical US county 39
Unhealthy days / yr better than typical
Montgomery County 0
Ashtabula County, Ohio 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Montgomery County (43), not geographic neighbors.
Ashtabula County, Ohio
Median AQI 43 · 81.2% Good-day share
Baltimore (City) County, Maryland
Median AQI 43 · 68.1% Good-day share
Bartholomew County, Indiana
Median AQI 43 · 72.6% Good-day share
Berks County, Pennsylvania
Median AQI 43 · 68.2% Good-day share
Bolivar County, Mississippi
Median AQI 43 · 71.9% Good-day share
Brewster County, Texas
Median AQI 43 · 74.7% Good-day share
Same primary pollutant: PM2.5
PM2.5 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).
Lenawee County, Michigan
69.3% Good-day share · median AQI 41
Sumner County, Tennessee
69.3% Good-day share · median AQI 44
Olmsted County, Minnesota
69.5% Good-day share · median AQI 39
Oakland County, Michigan
69.1% Good-day share · median AQI 41
Baker County, Florida
69.5% Good-day share · median AQI 44
Cabell County, West Virginia
69.5% Good-day share · median AQI 42
Iowa counties on the map
Geographic containment only, other monitored counties in Iowa, independent of AQI or pollutant match.
What Montgomery 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 43 means for exposure. Health guidance
- See how Montgomery County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Montgomery County with its Iowa neighbours before drawing a conclusion about the region. All of Iowa
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 Montgomery County, Iowa? ▼
Montgomery County has a median Air Quality Index (AQI) of 43, rated "Good." 69.3% of monitored days (253 out of 365) had good air quality in 2025.
What is the main pollutant in Montgomery County? ▼
The primary pollutant in Montgomery County is Fine Particles (PM2.5), which was the main AQI driver on 233 days (64% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Montgomery County have? ▼
In 2025, Montgomery County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 133.
Is the air quality in Montgomery County getting better or worse? ▼
Air quality in Montgomery 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 84.0% (305 of 363 days). Lowest qualifying Good-day share: 2023 at 62.1% (226 of 364 days).
What does AQI 43 mean for health? ▼
Montgomery County's median AQI of 43 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Montgomery County compare to other counties in Iowa? ▼
Montgomery County has 69.3% good air days. Nearby counties in Iowa: Black Hawk (53.4% good), Bremer (87.1% good), Clinton (59.5% good), Harrison (83.0% good), Johnson (70.1% good), Linn (61.4% good).
What is the 90th percentile AQI in Montgomery County? ▼
The 90th percentile AQI for Montgomery County is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 133 (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 Montgomery County, Iowa · 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.