Median AQI
44
Good
Michigan · County air quality · 2025
Allegan County, Michigan
Median AQI 44 (Good). 63.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 44
- Median AQI
- 63.9%
- Good-air days
- 2
- Unhealthy days
- 21%
- Cleaner than US counties
Allegan County's 2025 annual median AQI is 44 (Good), with 63.9% Good days
According to the U.S. EPA Air Quality System, Allegan County, Michigan posted a 2025 median AQI of 44 (Good) across 363 monitored days, with 63.9% rated Good and 2 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Allegan County's 63.9% Good-day share places it cleaner than 21% of US counties in 2025.
- Closest median-AQI peer
- Allen County (60.0% Good, median AQI 44) is the closest nationwide median-AQI peer to Allegan County.
- 2020–2025 trend
- Allegan County's floor-qualifying Good-day share is worsening from 2020 to 2025 (76.6% → 63.9%).
- Median AQI
- Median AQI: 44
The verdict
According to EPA Air Quality System monitoring data, Allegan County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 44 with 63.9% of 363 monitored days in the Good band, driven mainly by PM2.5.
- 44
- median AQI · Good
- 63.9%
- days rated Good
- PM2.5
- main pollutant
- 21%
- cleaner than US counties
2 days reached Unhealthy or worse; the worst single reading hit AQI 151.
Annual release change
What changed in the 2025 EPA annual release
- Allegan County's peak single-day AQI rose from 115 to 151 between the 2024 and 2025 EPA annual releases, a change of +36 points.
- Allegan County's Unhealthy-category days rose from 0 to 2 between the 2024 and 2025 EPA annual releases, a change of +2 days.
Data updated August 2026
- Good · 232 d · 63.9%
- Moderate · 117 d · 32.2%
- USG · 12 d · 3.3%
- Unhealthy · 2 d · 0.6%
How did Allegan County's air break down in 2025?
Across 363 monitored days, 232 fell in the Good band (AQI 0–50) and 2 reached Unhealthy or worse. The worst single day peaked at AQI 151 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 363 days monitored. Median AQI: 44 (Good).
Insights: Allegan County, Michigan. EPA monitors recorded a median Air Quality Index of 44 across 363 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 232 (64%) fell in the Good band (AQI 0–50), 117 (32%) registered Moderate readings, and 12 (3%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 75, while the worst single-day peak hit 151 (Unhealthy). Residents averaged about 19.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (202 days), Ozone (161 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -12.7 points and the median AQI moved +7 points, placing the multi-year trajectory at worsening. The annual record contains 2 days at Unhealthy or worse. On those days, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: 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); Genesee (83.2% good, AQI 38).
Air Quality Summary
Good Days
63.9%
232 of 363 monitored days
-11.1pp vs 75% target
Max AQI Recorded
151
Unhealthy
Health Grade
Moderate
90th-pct AQI 75
Allegan County, Good days share 63.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Allegan County, Unhealthy-or-worse share 5.5%
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 363 monitored days across EPA AQI categories.
Good
232
64%
Moderate
117
32%
USG
12
3%
Unhealthy
2
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Allegan County.
- PM2.5 · 202 days · 55.6%
- Ozone · 161 days · 44.4%
Health Impact Assessment
Moderate
Allegan County's air quality is rated Moderate based on 63.9% good air days. There were 2 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 12 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 151. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 202 of 363 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Allegan County. Highest Good-day share: 2020 (76.6%, 275 of 359 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 275 | 78 | 6 | 0 | 37 | 136 |
| 2021 | 245 | 107 | 9 | 0 | 42 | 136 |
| 2022 | 256 | 82 | 4 | 2 | 40 | 195 |
| 2023 | 246 | 102 | 11 | 1 | 42 | 161 |
| 2024 | 222 | 125 | 4 | 0 | 46 | 115 |
| 2025 | 232 | 117 | 12 | 2 | 44 | 151 |
How does Allegan County compare?
How Allegan County compares
Good-day share worse than typical
Allegan County 63.9%
Allen County, Indiana 60.0%
Typical US county 76.0%
Median AQI worse than typical
Allegan County 44
Allen County, Indiana 44
Typical US county 39
Unhealthy days / yr worse than typical
Allegan County 2
Allen County, Indiana 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Allegan County (44), not geographic neighbors.
Allen County, Indiana
Median AQI 44 · 60.0% Good-day share
Baker County, Florida
Median AQI 44 · 69.5% Good-day share
Bay County, Florida
Median AQI 44 · 66.4% Good-day share
Blount County, Tennessee
Median AQI 44 · 71.5% Good-day share
Cache County, Utah
Median AQI 44 · 66.0% Good-day share
Camden County, New Jersey
Median AQI 44 · 65.6% 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).
DuPage County, Illinois
63.8% Good-day share · median AQI 42
Erie County, New York
63.8% Good-day share · median AQI 44
Kings County, New York
63.8% Good-day share · median AQI 39
Hamilton County, Indiana
64.0% Good-day share · median AQI 44
Montgomery County, Alabama
63.8% Good-day share · median AQI 44
Marshall County, West Virginia
63.7% Good-day share · median AQI 42
Michigan counties on the map
Geographic containment only, other monitored counties in Michigan, independent of AQI or pollutant match.
What Allegan County's air means for you
On most days the air here is fine, but PM2.5 drives 2 unhealthy-or-worse days 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 44 means for exposure. Health guidance
- See how Allegan County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Allegan County with its Michigan neighbours before drawing a conclusion about the region. All of Michigan
Based on 363 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 Allegan County, Michigan? ▼
Allegan County has a median Air Quality Index (AQI) of 44, rated "Good." 63.9% of monitored days (232 out of 363) had good air quality in 2025.
What is the main pollutant in Allegan County? ▼
The primary pollutant in Allegan County is Fine Particles (PM2.5), which was the main AQI driver on 202 days (56% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Allegan County have? ▼
In 2025, Allegan County recorded 2 unhealthy air days (2 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 151.
Is the air quality in Allegan County getting better or worse? ▼
Air quality in Allegan 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 76.6% (275 of 359 days). Lowest qualifying Good-day share: 2024 at 63.2% (222 of 351 days).
What does AQI 44 mean for health? ▼
Allegan County's median AQI of 44 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Allegan County compare to other counties in Michigan? ▼
Allegan County has 63.9% good air days. Nearby counties in Michigan: Bay (70.4% good), Benzie (91.1% good), Berrien (80.9% good), Cass (85.3% good), Clinton (90.2% good), Genesee (83.2% good).
What is the 90th percentile AQI in Allegan County? ▼
The 90th percentile AQI for Allegan County is 75, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 151 (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 Allegan 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.