Median AQI
19
Good
Minnesota · County air quality · 2025
Winona County, Minnesota
Median AQI 19 (Good). 94.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 19
- Median AQI
- 94.1%
- Good-air days
- 0
- Unhealthy days
- 86%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Winona County's air is good on balance, cleaner than most US counties, a median AQI of 19 with 94.1% of 17 monitored days in the Good band, driven mainly by PM2.5.
- 19
- median AQI · Good
- 94.1%
- days rated Good
- PM2.5
- main pollutant
- 86%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 57.
Data updated July 2026
- Good · 16 d · 94.1%
- Moderate · 1 d · 5.9%
How did Winona County's air break down in 2025?
Across 17 monitored days, 16 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 57 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 17 days monitored. Median AQI: 19 (Good).
Insights: Winona County, Minnesota. EPA monitors recorded a median Air Quality Index of 19 across 17 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 16 (94%) fell in the Good band (AQI 0–50), 1 (6%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 49, while the worst single-day peak hit 57 (Moderate). Residents averaged about 28.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (17 days). Across the 2020–2025 trend window, good days shifted by -96 and the median AQI moved -3 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 57, moderate but never Unhealthy. Nearby counties show comparable readings: Anoka (82.1% good, AQI 38); Becker (84.7% good, AQI 38); Beltrami (88.8% good, AQI 37); Blue Earth (82.7% good, AQI 38); Carlton (92.9% good, AQI 35); Cass (94.4% good, AQI 22).
Air Quality Summary
Good Days
94.1%
16 of 17 monitored days
19.1pp vs 75% target
Max AQI Recorded
57
Moderate
Health Grade
Excellent
90th-pct AQI 49
Winona County, Good days share 94.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Winona 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 17 monitored days across EPA AQI categories.
Good
16
94%
Moderate
1
6%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Winona County.
- PM2.5 · 17 days · 100.0%
Health Impact Assessment
Excellent
Winona County's air quality is rated Excellent based on 94.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 94.1% of monitored days in 2025, with a median AQI of 19. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 17 of 17 monitored days.
5-Year Air Quality Trend
Air quality is stable in Winona County. Best year: 2024 (114 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 112 | 7 | 0 | 0 | 22 | 57 |
| 2021 | 101 | 15 | 0 | 0 | 24 | 80 |
| 2022 | 113 | 8 | 0 | 0 | 22 | 65 |
| 2023 | 95 | 22 | 1 | 1 | 28 | 169 |
| 2024 | 114 | 8 | 0 | 0 | 20 | 63 |
| 2025 | 16 | 1 | 0 | 0 | 19 | 57 |
How does Winona County compare?
How Winona County compares
Good-day share better than US avg
Winona County 94.1%
Anoka County, Minnesota 82.1%
US average 76.5%
Median AQI better than US avg
Winona County 19
Anoka County, Minnesota 38
US average 38
Unhealthy days / yr about average
Winona County 0
Anoka County, Minnesota 1
US average 0
Other Counties in Minnesota
Air quality comparison for nearby counties in Minnesota.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Winona County.
Adams County, Washington
AQI 19 · 94.7% good
Bonneville County, Idaho
AQI 19 · 94.9% good
Elko County, Nevada
AQI 19 · 90.8% good
Grays Harbor County, Washington
AQI 19 · 97.9% good
Jefferson County, Washington
AQI 19 · 96.5% good
Luna County, New Mexico
AQI 19 · 79.5% good
What Winona 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 19 means for exposure. Health guidance
- See how Winona County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Winona County with its Minnesota neighbours before drawing a conclusion about the region. All of Minnesota
Based on 17 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 Winona County, Minnesota? ▼
Winona County has a median Air Quality Index (AQI) of 19, rated "Good." 94.1% of monitored days (16 out of 17) had good air quality in 2025.
What is the main pollutant in Winona County? ▼
The primary pollutant in Winona County is Fine Particles (PM2.5), which was the main AQI driver on 17 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Winona County have? ▼
In 2025, Winona County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 57.
Is the air quality in Winona County getting better or worse? ▼
Air quality in Winona County is stable based on 5-year trends (2020-2025). Best year: 2024 with 114 good days. Worst year: 2025 with 16 good days.
What does AQI 19 mean for health? ▼
Winona County's median AQI of 19 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 Winona County compare to other counties in Minnesota? ▼
Winona County has 94.1% good air days. Nearby counties in Minnesota: Anoka (82.1% good), Becker (84.7% good), Beltrami (88.8% good), Blue Earth (82.7% good), Carlton (92.9% good), Cass (94.4% good).
What is the 90th percentile AQI in Winona County? ▼
The 90th percentile AQI for Winona County is 49, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 57 (Moderate).
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.