Median AQI
40
Good
Wisconsin · County air quality · 2025
Dane County, Wisconsin
Median AQI 40 (Good). 71.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 40
- Median AQI
- 71.8%
- Good-air days
- 0
- Unhealthy days
- 35%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Dane County's air is good on balance, more polluted than the median US county, a median AQI of 40 with 71.8% of 181 monitored days in the Good band, driven mainly by PM2.5.
- 40
- median AQI · Good
- 71.8%
- days rated Good
- PM2.5
- main pollutant
- 35%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 136.
Data updated July 2026
- Good · 130 d · 71.8%
- Moderate · 50 d · 27.6%
- USG · 1 d · 0.6%
How did Dane County's air break down in 2025?
Across 181 monitored days, 130 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 136 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 40 (Good).
Insights: Dane County, Wisconsin. EPA monitors recorded a median Air Quality Index of 40 across 181 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 130 (72%) fell in the Good band (AQI 0–50), 50 (28%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 61, while the worst single-day peak hit 136 (USG). Residents averaged about 21.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (121 days), Ozone (60 days). Across the 2020–2025 trend window, good days shifted by -92 and the median AQI moved -4 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 136, usg but never Unhealthy. Nearby counties show comparable readings: Ashland (85.6% good, AQI 39); Brown (79.0% good, AQI 37); Columbia (84.6% good, AQI 42); Dodge (76.4% good, AQI 39); Door (85.7% good, AQI 40); Eau Claire (77.9% good, AQI 38).
Air Quality Summary
Good Days
71.8%
130 of 181 monitored days
-3.2pp vs 75% target
Max AQI Recorded
136
USG
Health Grade
Moderate
90th-pct AQI 61
Dane County, Good days share 71.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Dane County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 181 monitored days across EPA AQI categories.
Good
130
72%
Moderate
50
28%
USG
1
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Dane County.
- PM2.5 · 121 days · 66.9%
- Ozone · 60 days · 33.1%
Health Impact Assessment
Moderate
Dane County's air quality is rated Moderate based on 71.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 71.8% of monitored days in 2025, with a median AQI of 40. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 121 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Dane County. Best year: 2024 (264 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 222 | 142 | 2 | 0 | 44 | 112 |
| 2021 | 199 | 165 | 1 | 0 | 48 | 101 |
| 2022 | 236 | 129 | 0 | 0 | 45 | 91 |
| 2023 | 184 | 157 | 20 | 1 | 50 | 268 |
| 2024 | 264 | 102 | 0 | 0 | 42 | 93 |
| 2025 | 130 | 50 | 1 | 0 | 40 | 136 |
How does Dane County compare?
How Dane County compares
Good-day share worse than US avg
Dane County 71.8%
Ashland County, Wisconsin 85.6%
US average 76.5%
Median AQI worse than US avg
Dane County 40
Ashland County, Wisconsin 39
US average 38
Unhealthy days / yr about average
Dane County 0
Ashland County, Wisconsin 1
US average 0
Other Counties in Wisconsin
Air quality comparison for nearby counties in Wisconsin.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Dane County.
Amador County, California
AQI 40 · 84.8% good
Anne Arundel County, Maryland
AQI 40 · 87.2% good
Arlington County, Virginia
AQI 40 · 84.8% good
Bergen County, New Jersey
AQI 40 · 71.1% good
Berkeley County, West Virginia
AQI 40 · 81.1% good
Billings County, North Dakota
AQI 40 · 80.3% good
What Dane County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 40 means for exposure. Health guidance
- See how Dane County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Dane County with its Wisconsin neighbours before drawing a conclusion about the region. All of Wisconsin
Based on 181 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Dane County, Wisconsin? ▼
Dane County has a median Air Quality Index (AQI) of 40, rated "Good." 71.8% of monitored days (130 out of 181) had good air quality in 2025.
What is the main pollutant in Dane County? ▼
The primary pollutant in Dane County is Fine Particles (PM2.5), which was the main AQI driver on 121 days (67% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Dane County have? ▼
In 2025, Dane County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 136.
Is the air quality in Dane County getting better or worse? ▼
Air quality in Dane County is improving based on 5-year trends (2020-2025). Best year: 2024 with 264 good days. Worst year: 2025 with 130 good days.
What does AQI 40 mean for health? ▼
Dane County's median AQI of 40 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Dane County compare to other counties in Wisconsin? ▼
Dane County has 71.8% good air days. Nearby counties in Wisconsin: Ashland (85.6% good), Brown (79.0% good), Columbia (84.6% good), Dodge (76.4% good), Door (85.7% good), Eau Claire (77.9% good).
What is the 90th percentile AQI in Dane County? ▼
The 90th percentile AQI for Dane County is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 136 (USG).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.