Median AQI
40
Good
Michigan · County air quality · 2025
Ottawa County, Michigan
Median AQI 40 (Good). 71.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 40
- Median AQI
- 71.2%
- Good-air days
- 1
- Unhealthy days
- 35%
- Cleaner than US counties
Ottawa County's 2025 annual median AQI is 40 (Good), with 71.2% Good days
According to the U.S. EPA Air Quality System, Ottawa County, Michigan posted a 2025 median AQI of 40 (Good) across 365 monitored days, with 71.2% rated Good and 1 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Ottawa County's 71.2% Good-day share places it cleaner than 35% of US counties in 2025.
- Closest median-AQI peer
- Anderson County (91.3% Good, median AQI 40) is the closest nationwide median-AQI peer to Ottawa County.
- 2020–2025 trend
- Ottawa County's floor-qualifying Good-day share is worsening from 2020 to 2025 (83.0% → 71.2%).
- Median AQI
- Median AQI: 40
The verdict
According to EPA Air Quality System monitoring data, Ottawa County's air is good on balance, more polluted than the median US county, a median AQI of 40 with 71.2% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 40
- median AQI · Good
- 71.2%
- days rated Good
- PM2.5
- main pollutant
- 35%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 159.
Annual release change
What changed in the 2025 EPA annual release
- Ottawa County's peak single-day AQI rose from 105 to 159 between the 2024 and 2025 EPA annual releases, a change of +54 points.
- Ottawa County's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.
Data updated August 2026
- Good · 260 d · 71.2%
- Moderate · 97 d · 26.6%
- USG · 7 d · 1.9%
- Unhealthy · 1 d · 0.3%
How did Ottawa County's air break down in 2025?
Across 365 monitored days, 260 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 159 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 40 (Good).
Insights: Ottawa County, Michigan. EPA monitors recorded a median Air Quality Index of 40 across 365 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 260 (71%) fell in the Good band (AQI 0–50), 97 (27%) registered Moderate readings, and 7 (2%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 68, while the worst single-day peak hit 159 (Unhealthy). Residents averaged about 21.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (209 days), Ozone (153 days), PM10 (3 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -11.8 points and the median AQI moved +5 points, placing the multi-year trajectory at worsening. The annual record contains 1 day at Unhealthy or worse. On that day, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Allegan (63.9% good, AQI 44); Bay (70.4% good, AQI 39); Benzie (91.1% good, AQI 35); Berrien (80.9% good, AQI 41); Cass (85.3% good, AQI 40); Clinton (90.2% good, AQI 39).
Air Quality Summary
Good Days
71.2%
260 of 365 monitored days
-3.8pp vs 75% target
Max AQI Recorded
159
Unhealthy
Health Grade
Moderate
90th-pct AQI 68
Ottawa County, Good days share 71.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Ottawa County, Unhealthy-or-worse share 2.7%
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
260
71%
Moderate
97
27%
USG
7
2%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Ottawa County.
- PM2.5 · 209 days · 57.3%
- Ozone · 153 days · 41.9%
- PM10 · 3 days · 0.8%
Health Impact Assessment
Moderate
Ottawa County's air quality is rated Moderate based on 71.2% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 7 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 159. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 209 of 365 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Ottawa County. Highest Good-day share: 2020 (83.0%, 303 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 303 | 56 | 6 | 0 | 35 | 150 |
| 2021 | 186 | 175 | 4 | 0 | 49 | 108 |
| 2022 | 194 | 134 | 2 | 2 | 46 | 164 |
| 2023 | 176 | 172 | 5 | 2 | 51 | 227 |
| 2024 | 257 | 107 | 1 | 0 | 41 | 105 |
| 2025 | 260 | 97 | 7 | 1 | 40 | 159 |
How does Ottawa County compare?
How Ottawa County compares
Good-day share worse than US avg
Ottawa County 71.2%
Anderson County, South Carolina 91.3%
US average 76.0%
Median AQI worse than US avg
Ottawa County 40
Anderson County, South Carolina 40
US average 39
Unhealthy days / yr about average
Ottawa County 1
Anderson County, South Carolina 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Ottawa County (40), not geographic neighbors.
Anderson County, South Carolina
Median AQI 40 · 91.3% Good-day share
Andrew County, Missouri
Median AQI 40 · 86.9% Good-day share
Anne Arundel County, Maryland
Median AQI 40 · 87.6% Good-day share
Bergen County, New Jersey
Median AQI 40 · 71.1% Good-day share
Blair County, Pennsylvania
Median AQI 40 · 76.9% Good-day share
Brazos County, Texas
Median AQI 40 · 68.5% 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).
Umatilla County, Oregon
71.2% Good-day share · median AQI 41
Kay County, Oklahoma
71.2% Good-day share · median AQI 37
Citrus County, Florida
71.1% Good-day share · median AQI 43
Lawrence County, Ohio
71.0% Good-day share · median AQI 42
Orleans County, Louisiana
71.0% Good-day share · median AQI 42
Cumberland County, Pennsylvania
71.5% Good-day share · median AQI 35
Michigan counties on the map
Geographic containment only, other monitored counties in Michigan, independent of AQI or pollutant match.
What Ottawa County's air means for you
On most days the air here is fine, but PM2.5 drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 40 means for exposure. Health guidance
- See how Ottawa County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Ottawa County with its Michigan neighbours before drawing a conclusion about the region. All of Michigan
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 Ottawa County, Michigan? ▼
Ottawa County has a median Air Quality Index (AQI) of 40, rated "Good." 71.2% of monitored days (260 out of 365) had good air quality in 2025.
What is the main pollutant in Ottawa County? ▼
The primary pollutant in Ottawa County is Fine Particles (PM2.5), which was the main AQI driver on 209 days (57% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Ottawa County have? ▼
In 2025, Ottawa County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 159.
Is the air quality in Ottawa County getting better or worse? ▼
Air quality in Ottawa 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: 2020 at 83.0% (303 of 365 days). Lowest qualifying Good-day share: 2023 at 49.6% (176 of 356 days).
What does AQI 40 mean for health? ▼
Ottawa County's median AQI of 40 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Ottawa County compare to other counties in Michigan? ▼
Ottawa County has 71.2% good air days. Nearby counties in Michigan: Allegan (63.9% good), Bay (70.4% good), Benzie (91.1% good), Berrien (80.9% good), Cass (85.3% good), Clinton (90.2% good).
What is the 90th percentile AQI in Ottawa County? ▼
The 90th percentile AQI for Ottawa County is 68, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 159 (Unhealthy).
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 Ottawa County, Michigan · 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.