Metro area air quality · 2025

Ann Arbor, MI

Median AQI 41 (Good). 69.3% of monitored days rated Good across this metro's EPA monitoring network.

41
Median AQI
69.3%
Good-air days
1
Unhealthy days
43%
Cleaner than US metros

Ann Arbor, MI posted a 2025 median AQI of 41 (Good) with 69.3% Good days

According to the U.S. EPA Air Quality System, the Ann Arbor, MI CBSA recorded a median AQI of 41 across 365 monitored days in 2025, with 69.3% rated Good and 1 unhealthy or worse. This is an annual metro comparison, not a live advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US metros
The Ann Arbor, MI CBSA's 69.3% Good-day share places it cleaner than 43% of US metros in 2025.
Closest median-AQI peer
Adrian, MI (69.3% Good, median AQI 41) is the closest nationwide median-AQI peer to Ann Arbor, MI.
2020–2025 Good-day shift
Ann Arbor, MI's Good-day share moved +5.3 points from 2020 to 2025 (median AQI -2).
Median AQI
Median AQI: 41

Aggregated from EPA Air Quality System (2025), 365 monitored days. EPA AQS →

The verdict

Ann Arbor, MI's peak reading 152 is in the upper max-AQI tercile among CBSA metros here. On the EPA scale the metro runs good, more polluted than the median US metro, with a median AQI of 41 and 69.3% of 365 monitored days in the Good band.

41
median AQI · Good
69.3%
days rated Good
43%
cleaner than US metros
152
worst single reading

1 day reached Unhealthy or worse across the metro's monitors in 2025.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Ann Arbor, MI metro's peak single-day AQI rose from 87 to 152 between the 2024 and 2025 EPA annual releases, a change of +65 points.
  • Ann Arbor, MI metro's Good-day share rose from 69.1% to 70.7% between the 2024 and 2025 EPA annual releases, a change of +1.5 percentage points.
  • Ann Arbor, MI metro's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.

Compared against 366 monitored days in 2024 and 358 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Ann Arbor, MI's peak reading 152 is in the upper max-AQI tercile among CBSA metros here. Signature read: peak AQI 152 (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 41 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 253 Good (69%), 104 Moderate (28%), and 7 Unhealthy-for-Sensitive-Groups (2%). The 90th-percentile AQI finished at 68; the highest single-day reading hit 152 (Unhealthy).

Across 2020–2025, Good-day share shifted +5.3 points and median AQI moved -2 (improving). The annual record contains 1 day at Unhealthy or worse. Metros with comparable AQI profiles include Adrian, MI (69.3% good, AQI 41); Albany-Schenectady-Troy, NY (67.7% good, AQI 41); Bowling Green, KY (75.6% good, AQI 41).

Health effects of air pollution →

Air Quality Summary

Median AQI

41

Good

Good Days

69.3%

253 of 365 days

Max AQI

152

Unhealthy

Health Grade

Moderate

90th pct: 68

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

253

69%

Moderate

104

28%

USG

7

2%

Unhealthy

1

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Ann Arbor, MI metro area's air quality is rated Moderate based on 69.3% 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" and peak AQI reached 152. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Ann Arbor, MI metro compare?

How Ann Arbor, MI compares

Good-day share worse than typical
Ann Arbor, MI 69.3%
Adrian, MI 69.3%
Typical US metro 70.6%
Median AQI about typical
Ann Arbor, MI 41
Adrian, MI 41
Typical US metro 41
Unhealthy days / yr about typical
Ann Arbor, MI 1
Adrian, MI 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Ann Arbor, MI metro. Highest Good-day share: 2025 (70.7%, 253 of 358 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 236 124 1 43
2021 212 153 0 46
2022 222 142 0 46
2023 168 184 2 52
2024 253 113 0 43
2025 253 104 1 41

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Ann Arbor, MI (41).

Adrian, MI

Median AQI 41 · 69.3% Good-day share

41

Albany-Schenectady-Troy, NY

Median AQI 41 · 67.7% Good-day share

41

Bowling Green, KY

Median AQI 41 · 75.6% Good-day share

41

Brunswick, GA

Median AQI 41 · 74.3% Good-day share

41

Decatur, AL

Median AQI 41 · 78.4% Good-day share

41

Dover, DE

Median AQI 41 · 75.6% Good-day share

41

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Ann Arbor, MI's 1 (independent of median AQI).

Bangor, ME

1 unhealthy-or-worse days · median AQI 33

33

Baraboo, WI

1 unhealthy-or-worse days · median AQI 35

35

Bartlesville, OK

1 unhealthy-or-worse days · median AQI 44

44

Beaumont-Port Arthur, TX

1 unhealthy-or-worse days · median AQI 52

52

Beaver Dam, WI

1 unhealthy-or-worse days · median AQI 40

40

Bellingham, WA

1 unhealthy-or-worse days · median AQI 31

31

Frequently Asked Questions

What is the 90th percentile AQI for Ann Arbor, MI? ▼
The 90th percentile AQI for the Ann Arbor, MI metro area is 68, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 152 (Unhealthy).
How many unhealthy air days does Ann Arbor, MI have? ▼
In 2025, the Ann Arbor, MI metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 152.
What is the air quality in the Ann Arbor, MI metro area? ▼
The Ann Arbor, MI metro area has a median Air Quality Index (AQI) of 41, rated "Good." 69.3% of monitored days (253 out of 365) had good air quality in 2025.
Is air quality in Ann Arbor, MI getting better or worse? ▼
Air quality in the Ann Arbor, MI metro is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2025 at 70.7% (253 of 358 days). Lowest qualifying Good-day share: 2023 at 47.5% (168 of 354 days).
What does AQI 41 mean for health? ▼
An AQI of 41 is "Good", air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
How does Ann Arbor, MI compare to other metro areas? ▼
The Ann Arbor, MI metro has 69.3% good air days. Similar metros: Adrian, MI (69.3% good), Albany-Schenectady-Troy, NY (67.7% good), Bowling Green, KY (75.6% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Ann Arbor, MI, 2025. See our methodology for how AQI, median, and coverage figures are computed.

Read our methodology , how this data is sourced, computed, and verified.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary, Ann Arbor, MI · 2020–2025