Median AQI
38
Good
Iowa · County air quality · 2025
Bremer County, Iowa
Median AQI 38 (Good). 87.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 38
- Median AQI
- 87.1%
- Good-air days
- 0
- Unhealthy days
- 70%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Bremer County's air is good on balance, cleaner than the median US county, a median AQI of 38 with 87.1% of 241 monitored days in the Good band, driven mainly by Ozone.
- 38
- median AQI · Good
- 87.1%
- days rated Good
- Ozone
- main pollutant
- 70%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 115.
Data updated July 2026
- Good · 210 d · 87.1%
- Moderate · 30 d · 12.4%
- USG · 1 d · 0.4%
How did Bremer County's air break down in 2025?
Across 241 monitored days, 210 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 115 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 241 days monitored. Median AQI: 38 (Good).
Insights: Bremer County, Iowa. EPA monitors recorded a median Air Quality Index of 38 across 241 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 210 (87%) fell in the Good band (AQI 0–50), 30 (12%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 115 (USG). Residents averaged about 26.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (241 days). Across the 2020–2025 trend window, good days shifted by -22 and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 115, usg but never Unhealthy. Nearby counties show comparable readings: Black Hawk (56.6% good, AQI 48); Clinton (59.9% good, AQI 45); Harrison (83.0% good, AQI 39); Johnson (71.0% good, AQI 36); Linn (61.2% good, AQI 44); Montgomery (68.8% good, AQI 43).
Air Quality Summary
Good Days
87.1%
210 of 241 monitored days
12.1pp vs 75% target
Max AQI Recorded
115
USG
Health Grade
Good
90th-pct AQI 54
Bremer County, Good days share 87.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Bremer 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 241 monitored days across EPA AQI categories.
Good
210
87%
Moderate
30
12%
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 Bremer County.
- Ozone · 241 days · 100.0%
Health Impact Assessment
Good
Bremer County's air quality is rated Good based on 87.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 87.1% of monitored days in 2025, with a median AQI of 38. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 241 of 241 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Bremer County. Best year: 2022 (235 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 232 | 12 | 0 | 0 | 35 | 87 |
| 2021 | 223 | 21 | 0 | 0 | 40 | 90 |
| 2022 | 235 | 8 | 0 | 0 | 37 | 67 |
| 2023 | 180 | 45 | 9 | 1 | 42 | 151 |
| 2024 | 207 | 27 | 0 | 0 | 40 | 74 |
| 2025 | 210 | 30 | 1 | 0 | 38 | 115 |
How does Bremer County compare?
How Bremer County compares
Good-day share better than US avg
Bremer County 87.1%
Black Hawk County, Iowa 56.6%
US average 76.5%
Median AQI about average
Bremer County 38
Black Hawk County, Iowa 48
US average 38
Unhealthy days / yr about average
Bremer 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 Bremer County.
Adams County, Illinois
AQI 38 · 94.4% good
Anoka County, Minnesota
AQI 38 · 82.1% good
Atlantic County, New Jersey
AQI 38 · 79.6% good
Avery County, North Carolina
AQI 38 · 93.9% good
Barnstable County, Massachusetts
AQI 38 · 92.5% good
Bay County, Michigan
AQI 38 · 71.8% good
What Bremer 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 38 means for exposure. Health guidance
- See how Bremer County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Bremer County with its Iowa neighbours before drawing a conclusion about the region. All of Iowa
Based on 241 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 Bremer County, Iowa? ▼
Bremer County has a median Air Quality Index (AQI) of 38, rated "Good." 87.1% of monitored days (210 out of 241) had good air quality in 2025.
What is the main pollutant in Bremer County? ▼
The primary pollutant in Bremer County is Ozone (O3), which was the main AQI driver on 241 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Bremer County have? ▼
In 2025, Bremer County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 115.
Is the air quality in Bremer County getting better or worse? ▼
Air quality in Bremer County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 235 good days. Worst year: 2023 with 180 good days.
What does AQI 38 mean for health? ▼
Bremer County's median AQI of 38 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 Bremer County compare to other counties in Iowa? ▼
Bremer County has 87.1% good air days. Nearby counties in Iowa: Black Hawk (56.6% good), Clinton (59.9% good), Harrison (83.0% good), Johnson (71.0% good), Linn (61.2% good), Montgomery (68.8% good).
What is the 90th percentile AQI in Bremer County? ▼
The 90th percentile AQI for Bremer County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 115 (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.