Median AQI
39
Good
Michigan · County air quality · 2025
Muskegon County, Michigan
Median AQI 39 (Good). 83.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 83.5%
- Good-air days
- 0
- Unhealthy days
- 65%
- Cleaner than US counties
Muskegon County's 2025 annual median AQI is 39 (Good), with 83.5% Good days
According to the U.S. EPA Air Quality System, Muskegon County, Michigan posted a 2025 median AQI of 39 (Good) across 243 monitored days, with 83.5% 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
- Muskegon County's 83.5% Good-day share places it cleaner than 65% of US counties in 2025.
- Closest median-AQI peer
- Aiken County (90.6% Good, median AQI 39) is the closest nationwide median-AQI peer to Muskegon County.
- 2020–2025 trend
- Muskegon County's floor-qualifying Good-day share is stable from 2020 to 2025 (84.7% → 83.5%).
- Median AQI
- Median AQI: 39
The verdict
According to EPA Air Quality System monitoring data, Muskegon County's air is good on balance, cleaner than the median US county, a median AQI of 39 with 83.5% of 243 monitored days in the Good band, driven mainly by Ozone.
- 39
- median AQI · Good
- 83.5%
- days rated Good
- Ozone
- main pollutant
- 65%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 140.
Annual release change
What changed in the 2025 EPA annual release
- Muskegon County's peak single-day AQI rose from 122 to 140 between the 2024 and 2025 EPA annual releases, a change of +18 points.
Data updated August 2026
- Good · 203 d · 83.5%
- Moderate · 38 d · 15.6%
- USG · 2 d · 0.8%
How did Muskegon County's air break down in 2025?
Across 243 monitored days, 203 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 140 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 243 days monitored. Median AQI: 39 (Good).
Insights: Muskegon County, Michigan. EPA monitors recorded a median Air Quality Index of 39 across 243 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 203 (84%) 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 61, while the worst single-day peak hit 140 (USG). Residents averaged about 25.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (243 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -1.1 points and the median AQI moved +2 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 140, usg but never Unhealthy. 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
83.5%
203 of 243 monitored days
8.5pp vs 75% target
Max AQI Recorded
140
USG
Health Grade
Good
90th-pct AQI 61
Muskegon County, Good days share 83.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Muskegon 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 243 monitored days across EPA AQI categories.
Good
203
84%
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 Muskegon County.
- Ozone · 243 days · 100.0%
Health Impact Assessment
Good
Muskegon County's air quality is rated Good based on 83.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 83.5% 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 243 of 243 monitored days.
5-Year Air Quality Trend
Air quality is stable in Muskegon County. Highest Good-day share: 2022 (86.8%, 211 of 243 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 210 | 32 | 6 | 0 | 37 | 143 |
| 2021 | 209 | 48 | 8 | 0 | 40 | 129 |
| 2022 | 211 | 25 | 5 | 2 | 37 | 187 |
| 2023 | 187 | 44 | 11 | 0 | 41 | 147 |
| 2024 | 203 | 36 | 4 | 0 | 38 | 122 |
| 2025 | 203 | 38 | 2 | 0 | 39 | 140 |
How does Muskegon County compare?
How Muskegon County compares
Good-day share better than US avg
Muskegon County 83.5%
Aiken County, South Carolina 90.6%
US average 76.0%
Median AQI about average
Muskegon County 39
Aiken County, South Carolina 39
US average 39
Unhealthy days / yr better than US avg
Muskegon County 0
Aiken County, South Carolina 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Muskegon County (39), not geographic neighbors.
Aiken County, South Carolina
Median AQI 39 · 90.6% Good-day share
Albany County, New York
Median AQI 39 · 68.5% Good-day share
Anderson County, Tennessee
Median AQI 39 · 94.3% Good-day share
Bay County, Michigan
Median AQI 39 · 70.4% Good-day share
Berkeley County, West Virginia
Median AQI 39 · 83.6% Good-day share
Boyd County, Kentucky
Median AQI 39 · 80.0% Good-day share
Same primary pollutant: Ozone
Ozone 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).
Grafton County, New Hampshire
83.6% Good-day share · median AQI 36
Jasper County, Missouri
83.6% Good-day share · median AQI 38
Osceola County, Florida
83.6% Good-day share · median AQI 40
Bennington County, Vermont
83.6% Good-day share · median AQI 37
Hood County, Texas
83.4% Good-day share · median AQI 38
Tolland County, Connecticut
83.7% Good-day share · median AQI 40
Michigan counties on the map
Geographic containment only, other monitored counties in Michigan, independent of AQI or pollutant match.
What Muskegon 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 Muskegon County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Muskegon County with its Michigan neighbours before drawing a conclusion about the region. All of Michigan
Based on 243 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 Muskegon County, Michigan? ▼
Muskegon County has a median Air Quality Index (AQI) of 39, rated "Good." 83.5% of monitored days (203 out of 243) had good air quality in 2025.
What is the main pollutant in Muskegon County? ▼
The primary pollutant in Muskegon County is Ozone (O3), which was the main AQI driver on 243 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Muskegon County have? ▼
In 2025, Muskegon County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 140.
Is the air quality in Muskegon County getting better or worse? ▼
Air quality in Muskegon County is stable 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 86.8% (211 of 243 days). Lowest qualifying Good-day share: 2023 at 77.3% (187 of 242 days).
What does AQI 39 mean for health? ▼
Muskegon County's median AQI of 39 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Muskegon County compare to other counties in Michigan? ▼
Muskegon County has 83.5% 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 Muskegon County? ▼
The 90th percentile AQI for Muskegon County is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 140 (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 Muskegon 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.