Air quality · ZIP 48104
Air quality in Ann Arbor, MI
In 2025, Washtenaw County, Michigan — the county ZIP 48104 is in — had a median daily AQI of 41, which EPA rates Good. Of 365 days with a reading, 253 were Good, 104 Moderate, 7 Unhealthy for Sensitive Groups and 1 Unhealthy or worse. This is EPA's annual county summary, not today's air.
Washtenaw County, Michigan · 2025 annual summary
Median AQI 41 — Good
Air quality is satisfactory, and air pollution poses little or no risk.
- Good days
- 253
- Moderate days
- 104
- Unhealthy for sensitive groups
- 7
- Unhealthy+ days
- 1
- Max AQI
- 152
- 90th percentile AQI
- 68
This is a county-level ANNUAL SUMMARY for 2025, not a live current reading. For today's air quality, check a real-time monitor at airnow.gov. Categories follow EPA's official AQI breakpoints.
Next step for your own home
What this page shows
The 2025 annual EPA Air Quality System summary for this ZIP's county — shown above.
Source & refresh
EPA Air Quality System (AQS), annual county summary. The figures are EPA's 2025 annual county summary. EPA publishes one summary a year, so this is not today's air. Primary source →
Limitations specific to this source
This is a county-level ANNUAL SUMMARY, not a live current reading and not an address-level measurement — for today's AQI, EPA's real-time AirNow feed is the correct source (not yet federated here). Not every county operates an EPA monitor; absence of data for a ZIP's county means no 2025 EPA reading exists, not that air is good.
Michigan context
Lead pipes (post-Flint), Great Lakes erosion
Michigan's LCRR obligations are among the heaviest in the US — Detroit, Flint, Benton Harbor, Lansing all carry significant lead-service-line replacement commitments. Great Lakes shoreline erosion expands FEMA AE zones in some lakefront counties.
See Michigan state page for the full state-level rollup across all 12 dimensions.
Read more on air quality
Editorial deep-dives explaining the source data, its limits, and how to read it.
EPA AQI categories explained — what 0–50 Good through 301–500 Hazardous mean
Plain-English guide to the six EPA Air Quality Index categories: 0–50 Good, 51–100 Moderate, 101–150 Unhealthy for Sensitive Groups, 151–200 Unhealthy, 201–300 Very Unhealthy, 301–500 Hazardous — what each level means and who is at risk.
AQI explained — what 50, 100, 150 actually mean for your lungs
Plain-English guide to the EPA Air Quality Index (AQI) and the 6 categories from Good to Hazardous. When to take precautions and which pollutants matter.
Wildfire Hazard Potential — what the USFS scale means and how to defend your home
Plain-English guide to the USDA Forest Service's Wildfire Hazard Potential 1–5 scale, how to read your community's risk, and concrete home-defense measures.
AirNow + wildfire smoke — when AQI is a real-time tool
How EPA AirNow handles real-time wildfire smoke, what the colors mean during fire season, and where AirNow leaves gaps you should know about.
The other dimensions for ZIP 48104
Air quality is one of twelve public-records dimensions zipradar indexes per address. See the ZIP 48104 index for the other eleven — each with its own regulator, source and link:
All dimensions for Ann Arbor, MI →Frequently asked questions
What is the air quality for ZIP 48104?
Washtenaw County, Michigan (which covers ZIP 48104) had a 2025 median AQI of 41 — Good, per EPA's Air Quality System. Over the year: 253 Good days, 104 Moderate, 7 Unhealthy for Sensitive Groups. This is a county-level ANNUAL SUMMARY for 2025, not a live current reading. For today's air quality, check a real-time monitor at airnow.gov. Categories follow EPA's official AQI breakpoints.
Where does the air quality data come from?
Source: EPA Air Quality System (AQS), annual county summary. The figures are EPA's 2025 annual county summary. EPA publishes one summary a year, so this is not today's air. The original is at https://aqs.epa.gov/aqsweb/airdata/download_files.html.
What are the limitations of air quality data?
This is a county-level ANNUAL SUMMARY, not a live current reading and not an address-level measurement — for today's AQI, EPA's real-time AirNow feed is the correct source (not yet federated here). Not every county operates an EPA monitor; absence of data for a ZIP's county means no 2025 EPA reading exists, not that air is good.
Is ZIP 48104 (Ann Arbor) data current?
zipradar last checked this page against the source on 2026-09-24. The figures are EPA's 2025 annual county summary. EPA publishes one summary a year, so this is not today's air. The ZIP 48104 overview at /zip/48104/ lists the other topics zipradar covers for this ZIP.