Metro area air quality · 2025

Appleton, WI

Median AQI 38 (Good). 72.3% of monitored days rated Good across this metro's EPA monitoring network.

38
Median AQI
72.3%
Good-air days
6
Unhealthy days
50%
Cleaner than US metros

Appleton, WI posted a 2025 median AQI of 38 (Good) with 72.3% Good days

According to the U.S. EPA Air Quality System, the Appleton, WI CBSA recorded a median AQI of 38 across 365 monitored days in 2025, with 72.3% rated Good and 6 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 Appleton, WI CBSA's 72.3% Good-day share places it cleaner than 50% of US metros in 2025.
Closest median-AQI peer
Billings, MT (86.3% Good, median AQI 38) is the closest nationwide median-AQI peer to Appleton, WI.
2020–2025 Good-day shift
Appleton, WI's Good-day share moved +3.1 points from 2020 to 2025 (median AQI -2).
Median AQI
Median AQI: 38

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

The verdict

Appleton, WI's peak reading 172 is in the upper max-AQI tercile among CBSA metros here. On the EPA scale the metro runs good, cleaner than the median US metro, with a median AQI of 38 and 72.3% of 365 monitored days in the Good band.

38
median AQI · Good
72.3%
days rated Good
50%
cleaner than US metros
172
worst single reading

6 days reached Unhealthy or worse across the metro's monitors in 2025.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Appleton, WI metro's peak single-day AQI rose from 99 to 172 between the 2024 and 2025 EPA annual releases, a change of +73 points.
  • Appleton, WI metro's Good-day share fell from 79.5% to 72.9% between the 2024 and 2025 EPA annual releases, a change of -6.6 percentage points.
  • Appleton, WI metro's Unhealthy-category days rose from 0 to 6 between the 2024 and 2025 EPA annual releases, a change of +6 days.

Compared against 366 monitored days in 2024 and 362 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

Appleton, WI's peak reading 172 is in the upper max-AQI tercile among CBSA metros here. Signature read: peak AQI 172 (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 38 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 264 Good (72%), 92 Moderate (25%), and 3 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 64; the highest single-day reading hit 172 (Unhealthy).

Across 2020–2025, Good-day share shifted +3.1 points and median AQI moved -2 (improving). The annual record contains 6 days at Unhealthy or worse. Metros with comparable AQI profiles include Billings, MT (86.3% good, AQI 38); Burlington-South Burlington, VT (87.7% good, AQI 38); Charlottesville, VA (81.0% good, AQI 38).

Health effects of air pollution →

Air Quality Summary

Median AQI

38

Good

Good Days

72.3%

264 of 365 days

Max AQI

172

Unhealthy

Health Grade

Moderate

90th pct: 64

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

264

72%

Moderate

92

25%

USG

3

1%

Unhealthy

6

2%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Appleton, WI metro area's air quality is rated Moderate based on 72.3% good air days. There were 6 unhealthy days in 2025 when outdoor activity should be limited.

Air quality is acceptable most days, but 3 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 172. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Appleton, WI metro compare?

How Appleton, WI compares

Good-day share better than typical
Appleton, WI 72.3%
Billings, MT 86.3%
Typical US metro 70.6%
Median AQI better than typical
Appleton, WI 38
Billings, MT 38
Typical US metro 41
Unhealthy days / yr worse than typical
Appleton, WI 6
Billings, MT 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Appleton, WI metro. Highest Good-day share: 2024 (79.5%, 291 of 366 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 254 110 0 40
2021 226 134 0 44
2022 241 123 0 43
2023 195 152 5 48
2024 291 75 0 37
2025 264 92 6 38

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Appleton, WI (38).

Billings, MT

Median AQI 38 · 86.3% Good-day share

38

Burlington-South Burlington, VT

Median AQI 38 · 87.7% Good-day share

38

Charlottesville, VA

Median AQI 38 · 81.0% Good-day share

38

Corning, NY

Median AQI 38 · 83.3% Good-day share

38

Dickinson, ND

Median AQI 38 · 82.7% Good-day share

38

Eau Claire, WI

Median AQI 38 · 73.7% Good-day share

38

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Appleton, WI's 6 (independent of median AQI).

Chicago-Naperville-Elgin, IL-IN-WI

6 unhealthy-or-worse days · median AQI 56

56

Marquette, MI

6 unhealthy-or-worse days · median AQI 19

19

Minneapolis-St. Paul-Bloomington, MN-WI

6 unhealthy-or-worse days · median AQI 47

47

Spokane-Spokane Valley, WA

6 unhealthy-or-worse days · median AQI 47

47

Dallas-Fort Worth-Arlington, TX

5 unhealthy-or-worse days · median AQI 59

59

Fargo, ND-MN

7 unhealthy-or-worse days · median AQI 37

37

Frequently Asked Questions

What is the 90th percentile AQI for Appleton, WI? ▼
The 90th percentile AQI for the Appleton, WI metro area is 64, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 172 (Unhealthy).
How many unhealthy air days does Appleton, WI have? ▼
In 2025, the Appleton, WI metro area recorded 6 unhealthy air days (6 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 172.
What is the air quality in the Appleton, WI metro area? ▼
The Appleton, WI metro area has a median Air Quality Index (AQI) of 38, rated "Good." 72.3% of monitored days (264 out of 365) had good air quality in 2025.
Is air quality in Appleton, WI getting better or worse? ▼
Air quality in the Appleton, 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 79.5% (291 of 366 days). Lowest qualifying Good-day share: 2023 at 55.4% (195 of 352 days).
What does AQI 38 mean for health? ▼
An AQI of 38 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 Appleton, WI compare to other metro areas? ▼
The Appleton, WI metro has 72.3% good air days. Similar metros: Billings, MT (86.3% good), Burlington-South Burlington, VT (87.7% good), Charlottesville, VA (81.0% good).

Data Sources

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