Metro area air quality · 2025

Madison, WI

Median AQI 42 (Good). 66.3% of monitored days rated Good across this metro's EPA monitoring network.

42
Median AQI
66.3%
Good-air days
1
Unhealthy days
37%
Cleaner than US metros

Madison, WI posted a 2025 median AQI of 42 (Good) with 66.3% Good days

According to the U.S. EPA Air Quality System, the Madison, WI CBSA recorded a median AQI of 42 across 365 monitored days in 2025, with 66.3% 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 Madison, WI CBSA's 66.3% Good-day share places it cleaner than 37% of US metros in 2025.
Closest median-AQI peer
Allentown-Bethlehem-Easton, PA-NJ (66.8% Good, median AQI 42) is the closest nationwide median-AQI peer to Madison, WI.
2020–2025 Good-day shift
Madison, WI's Good-day share moved +6.2 points from 2020 to 2025 (median AQI -3).
Median AQI
Median AQI: 42

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

The verdict

Madison, WI's peak reading 170 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 42 and 66.3% of 365 monitored days in the Good band.

42
median AQI · Good
66.3%
days rated Good
37%
cleaner than US metros
170
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
  • Madison, WI metro's peak single-day AQI rose from 93 to 170 between the 2024 and 2025 EPA annual releases, a change of +77 points.
  • Madison, WI metro's Good-day share fell from 71.6% to 67.4% between the 2024 and 2025 EPA annual releases, a change of -4.2 percentage points.
  • Madison, WI 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 359 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

Madison, WI's peak reading 170 is in the upper max-AQI tercile among CBSA metros here. Signature read: peak AQI 170 (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 42 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 242 Good (66%), 116 Moderate (32%), and 6 Unhealthy-for-Sensitive-Groups (2%). The 90th-percentile AQI finished at 66; the highest single-day reading hit 170 (Unhealthy).

Across 2020–2025, Good-day share shifted +6.2 points and median AQI moved -3 (improving). The annual record contains 1 day at Unhealthy or worse. Metros with comparable AQI profiles include Allentown-Bethlehem-Easton, PA-NJ (66.8% good, AQI 42); Amarillo, TX (78.4% good, AQI 42); Carson City, NV (86.2% good, AQI 42).

Health effects of air pollution →

Air Quality Summary

Median AQI

42

Good

Good Days

66.3%

242 of 365 days

Max AQI

170

Unhealthy

Health Grade

Moderate

90th pct: 66

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

242

66%

Moderate

116

32%

USG

6

2%

Unhealthy

1

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Madison, WI metro area's air quality is rated Moderate based on 66.3% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.

Air quality is acceptable most days, but 6 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 170. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Madison, WI metro compare?

How Madison, WI compares

Good-day share worse than typical
Madison, WI 66.3%
Allentown-Bethlehem-Easton, PA-NJ 66.8%
Typical US metro 70.6%
Median AQI worse than typical
Madison, WI 42
Allentown-Bethlehem-Easton, PA-NJ 42
Typical US metro 41
Unhealthy days / yr about typical
Madison, WI 1
Allentown-Bethlehem-Easton, PA-NJ 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Madison, WI metro. Highest Good-day share: 2024 (71.6%, 262 of 366 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 221 140 0 45
2021 197 167 0 48
2022 235 130 0 45
2023 181 159 2 51
2024 262 104 0 42
2025 242 116 1 42

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Madison, WI (42).

Allentown-Bethlehem-Easton, PA-NJ

Median AQI 42 · 66.8% Good-day share

42

Amarillo, TX

Median AQI 42 · 78.4% Good-day share

42

Carson City, NV

Median AQI 42 · 86.2% Good-day share

42

Casper, WY

Median AQI 42 · 86.3% Good-day share

42

Clarksville, TN-KY

Median AQI 42 · 72.0% Good-day share

42

Daphne-Fairhope-Foley, AL

Median AQI 42 · 75.5% Good-day share

42

Metros with similar unhealthy-day exposure

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

Ann Arbor, MI

1 unhealthy-or-worse days · median AQI 41

41

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

Frequently Asked Questions

What is the 90th percentile AQI for Madison, WI? ▼
The 90th percentile AQI for the Madison, WI metro area is 66, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 170 (Unhealthy).
How many unhealthy air days does Madison, WI have? ▼
In 2025, the Madison, WI metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 170.
What is the air quality in the Madison, WI metro area? ▼
The Madison, WI metro area has a median Air Quality Index (AQI) of 42, rated "Good." 66.3% of monitored days (242 out of 365) had good air quality in 2025.
Is air quality in Madison, WI getting better or worse? ▼
Air quality in the Madison, WI 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: 2024 at 71.6% (262 of 366 days). Lowest qualifying Good-day share: 2023 at 52.9% (181 of 342 days).
What does AQI 42 mean for health? ▼
An AQI of 42 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 Madison, WI compare to other metro areas? ▼
The Madison, WI metro has 66.3% good air days. Similar metros: Allentown-Bethlehem-Easton, PA-NJ (66.8% good), Amarillo, TX (78.4% good), Carson City, NV (86.2% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Madison, WI, 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, Madison, WI · 2020–2025