Metro area air quality · 2025

Beaver Dam, WI

Median AQI 40 (Good). 72.3% of monitored days rated Good across this metro's EPA monitoring network.

40
Median AQI
72.3%
Good-air days
1
Unhealthy days
50%
Cleaner than US metros

Beaver Dam, WI posted a 2025 median AQI of 40 (Good) with 72.3% Good days

According to the U.S. EPA Air Quality System, the Beaver Dam, WI CBSA recorded a median AQI of 40 across 365 monitored days in 2025, with 72.3% 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 Beaver Dam, WI CBSA's 72.3% Good-day share places it cleaner than 50% of US metros in 2025.
Closest median-AQI peer
Altoona, PA (76.9% Good, median AQI 40) is the closest nationwide median-AQI peer to Beaver Dam, WI.
2020–2025 Good-day shift
Beaver Dam, WI's Good-day share moved +5.7 points from 2020 to 2025 (median AQI -2).
Median AQI
Median AQI: 40

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

The verdict

Beaver Dam, WI's peak reading 171 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 40 and 72.3% of 365 monitored days in the Good band.

40
median AQI · Good
72.3%
days rated Good
50%
cleaner than US metros
171
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
  • Beaver Dam, WI metro's peak single-day AQI rose from 84 to 171 between the 2024 and 2025 EPA annual releases, a change of +87 points.
  • Beaver Dam, WI metro's Good-day share fell from 81.1% to 73.5% between the 2024 and 2025 EPA annual releases, a change of -7.6 percentage points.
  • Beaver Dam, 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

Beaver Dam, WI's peak reading 171 is in the upper max-AQI tercile among CBSA metros here. Signature read: peak AQI 171 (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 40 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 264 Good (72%), 94 Moderate (26%), and 6 Unhealthy-for-Sensitive-Groups (2%). The 90th-percentile AQI finished at 63; the highest single-day reading hit 171 (Unhealthy).

Across 2020–2025, Good-day share shifted +5.7 points and median AQI moved -2 (improving). The annual record contains 1 day at Unhealthy or worse. Metros with comparable AQI profiles include Altoona, PA (76.9% good, AQI 40); Bismarck, ND (76.7% good, AQI 40); Cape Coral-Fort Myers, FL (76.4% good, AQI 40).

Health effects of air pollution →

Air Quality Summary

Median AQI

40

Good

Good Days

72.3%

264 of 365 days

Max AQI

171

Unhealthy

Health Grade

Moderate

90th pct: 63

AQI Day Breakdown (2025)

Distribution of 365 monitored days across EPA AQI categories.

Good

264

72%

Moderate

94

26%

USG

6

2%

Unhealthy

1

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Beaver Dam, WI metro area's air quality is rated Moderate based on 72.3% 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 171. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Beaver Dam, WI metro compare?

How Beaver Dam, WI compares

Good-day share better than typical
Beaver Dam, WI 72.3%
Altoona, PA 76.9%
Typical US metro 70.6%
Median AQI better than typical
Beaver Dam, WI 40
Altoona, PA 40
Typical US metro 41
Unhealthy days / yr about typical
Beaver Dam, WI 1
Altoona, PA 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is improving in the Beaver Dam, WI metro. Highest Good-day share: 2024 (81.1%, 297 of 366 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 247 117 0 42
2021 216 149 0 46
2022 266 99 0 42
2023 213 133 2 46
2024 297 69 0 38
2025 264 94 1 40

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Beaver Dam, WI (40).

Altoona, PA

Median AQI 40 · 76.9% Good-day share

40

Bismarck, ND

Median AQI 40 · 76.7% Good-day share

40

Cape Coral-Fort Myers, FL

Median AQI 40 · 76.4% Good-day share

40

College Station-Bryan, TX

Median AQI 40 · 68.5% Good-day share

40

Fallon, NV

Median AQI 40 · 85.2% Good-day share

40

Fayetteville-Springdale-Rogers, AR-MO

Median AQI 40 · 83.3% Good-day share

40

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Beaver Dam, 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

Bellingham, WA

1 unhealthy-or-worse days · median AQI 31

31

Frequently Asked Questions

What is the 90th percentile AQI for Beaver Dam, WI? ▼
The 90th percentile AQI for the Beaver Dam, WI metro area is 63, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 171 (Unhealthy).
How many unhealthy air days does Beaver Dam, WI have? ▼
In 2025, the Beaver Dam, WI metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 171.
What is the air quality in the Beaver Dam, WI metro area? ▼
The Beaver Dam, WI metro area has a median Air Quality Index (AQI) of 40, rated "Good." 72.3% of monitored days (264 out of 365) had good air quality in 2025.
Is air quality in Beaver Dam, WI getting better or worse? ▼
Air quality in the Beaver Dam, 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 81.1% (297 of 366 days). Lowest qualifying Good-day share: 2021 at 59.2% (216 of 365 days).
What does AQI 40 mean for health? ▼
An AQI of 40 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 Beaver Dam, WI compare to other metro areas? ▼
The Beaver Dam, WI metro has 72.3% good air days. Similar metros: Altoona, PA (76.9% good), Bismarck, ND (76.7% good), Cape Coral-Fort Myers, FL (76.4% good).

Data Sources

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