Metro area air quality · 2025
Janesville-Beloit, WI
Median AQI 42 (Good). 79.9% of monitored days rated Good across this metro's EPA monitoring network.
- 42
- Median AQI
- 79.9%
- Good-air days
- 0
- Unhealthy days
- 67%
- Cleaner than US metros
Janesville-Beloit, WI posted a 2025 median AQI of 42 (Good) with 79.9% Good days
According to the U.S. EPA Air Quality System, the Janesville-Beloit, WI CBSA recorded a median AQI of 42 across 199 monitored days in 2025, with 79.9% rated Good and 0 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 Janesville-Beloit, WI CBSA's 79.9% Good-day share places it cleaner than 67% 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 Janesville-Beloit, WI.
- 2020–2025 Good-day shift
- Janesville-Beloit, WI's Good-day share moved -12.5 points from 2020 to 2025 (median AQI +4).
- Median AQI
- Median AQI: 42
Aggregated from EPA Air Quality System (2025), 199 monitored days. EPA AQS →
The verdict
Janesville-Beloit, WI's Good-day share (79.9%) sits in the middle CBSA tercile on this extract. On the EPA scale the metro runs good, cleaner than the median US metro, with a median AQI of 42 and 79.9% of 199 monitored days in the Good band.
- 42
- median AQI · Good
- 79.9%
- days rated Good
- 67%
- cleaner than US metros
- 108
- worst single reading
No day crossed into the Unhealthy tier across the metro's monitors in 2025.
Annual release change
What changed in the 2025 EPA annual release
- Janesville-Beloit, WI metro's Good-day share fell from 84.2% to 80.3% between the 2024 and 2025 EPA annual releases, a change of -3.9 percentage points.
Janesville-Beloit, WI's Good-day share (79.9%) sits in the middle CBSA tercile on this extract. Signature read: 79.9% Good-day share (mid tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 42 over 199 measured days in 2025 (Good / Good). The monitored-day split lands at 159 Good (80%), 39 Moderate (20%), and 1 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 61; the highest single-day reading hit 108 (USG).
Across 2020–2025, Good-day share shifted -12.5 points and median AQI moved +4 (worsening). No Unhealthy-tier days appear in this annual dataset. 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).
Air Quality Summary
Median AQI
42
Good
Good Days
79.9%
159 of 199 days
Max AQI
108
USG
Health Grade
Good
90th pct: 61
AQI Day Breakdown (2025)
Distribution of 199 monitored days across EPA AQI categories.
Good
159
80%
Moderate
39
20%
USG
1
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Health Impact Assessment
The Janesville-Beloit, WI metro area's air quality is rated Good based on 79.9% good air days. No unhealthy air days were recorded in 2025.
Air quality is generally acceptable. Unusually sensitive people should monitor real-time conditions at AirNow.gov during high-pollution events.
How does the Janesville-Beloit, WI metro compare?
How Janesville-Beloit, WI compares
5-Year Air Quality Trend
Air quality is worsening in the Janesville-Beloit, WI metro. Highest Good-day share: 2020 (92.8%, 192 of 207 monitored days).
| Year | Good | Moderate | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|
| 2020 | 192 | 15 | 0 | 38 | 105 |
| 2021 | 173 | 32 | 0 | 41 | 100 |
| 2022 | 184 | 18 | 0 | 39 | 97 |
| 2023 | 131 | 52 | 2 | 46 | 177 |
| 2024 | 171 | 32 | 0 | 41 | 112 |
| 2025 | 159 | 39 | 0 | 42 | 108 |
Metros with a similar median AQI
CBSA peers nationwide whose annual median AQI sits near Janesville-Beloit, WI (42).
Allentown-Bethlehem-Easton, PA-NJ
Median AQI 42 · 66.8% Good-day share
Amarillo, TX
Median AQI 42 · 78.4% Good-day share
Carson City, NV
Median AQI 42 · 86.2% Good-day share
Casper, WY
Median AQI 42 · 86.3% Good-day share
Clarksville, TN-KY
Median AQI 42 · 72.0% Good-day share
Daphne-Fairhope-Foley, AL
Median AQI 42 · 75.5% Good-day share
Metros with similar unhealthy-day exposure
A second relationship type: metros whose unhealthy-or-worse day count is closest to Janesville-Beloit, WI's 0 (independent of median AQI).
Aberdeen, SD
0 unhealthy-or-worse days · median AQI 27
Aberdeen, WA
0 unhealthy-or-worse days · median AQI 22
Adrian, MI
0 unhealthy-or-worse days · median AQI 41
Akron, OH
0 unhealthy-or-worse days · median AQI 45
Albany, GA
0 unhealthy-or-worse days · median AQI 46
Albany, OR
0 unhealthy-or-worse days · median AQI 27
Frequently Asked Questions
How many unhealthy air days does Janesville-Beloit, WI have? ▼
What is the air quality in the Janesville-Beloit, WI metro area? ▼
Is air quality in Janesville-Beloit, WI getting better or worse? ▼
What does AQI 42 mean for health? ▼
How does Janesville-Beloit, WI compare to other metro areas? ▼
What is the 90th percentile AQI for Janesville-Beloit, WI? ▼
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Janesville-Beloit, 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, Janesville-Beloit, WI · 2020–2025