Median AQI
39
Good
Minnesota · County air quality · 2025
Olmsted County, Minnesota
Median AQI 39 (Good). 69.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 69.5%
- Good-air days
- 3
- Unhealthy days
- 31%
- Cleaner than US counties
Olmsted County's 2025 annual median AQI is 39 (Good), with 69.5% Good days
According to the U.S. EPA Air Quality System, Olmsted County, Minnesota posted a 2025 median AQI of 39 (Good) across 344 monitored days, with 69.5% rated Good and 3 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Olmsted County's 69.5% Good-day share places it cleaner than 31% of US counties in 2025.
- Closest median-AQI peer
- Aiken County (90.6% Good, median AQI 39) is the closest nationwide median-AQI peer to Olmsted County.
- 2020–2025 trend
- Olmsted County's floor-qualifying Good-day share is worsening from 2020 to 2025 (79.8% → 69.5%).
- Median AQI
- Median AQI: 39
The verdict
According to EPA Air Quality System monitoring data, Olmsted County's air is good on balance, more polluted than the median US county, a median AQI of 39 with 69.5% of 344 monitored days in the Good band, driven mainly by PM2.5.
- 39
- median AQI · Good
- 69.5%
- days rated Good
- PM2.5
- main pollutant
- 31%
- cleaner than US counties
3 days reached Unhealthy or worse; the worst single reading hit AQI 166.
Annual release change
What changed in the 2025 EPA annual release
- Olmsted County's Good-day share rose from 63.9% to 69.5% between the 2024 and 2025 EPA annual releases, a change of +5.5 percentage points.
- Olmsted County's Unhealthy-category days rose from 1 to 3 between the 2024 and 2025 EPA annual releases, a change of +2 days.
- Olmsted County's median AQI fell from 44 to 39 between the 2024 and 2025 EPA annual releases, a change of -5 points.
- Olmsted County's peak single-day AQI rose from 155 to 166 between the 2024 and 2025 EPA annual releases, a change of +11 points.
Data updated August 2026
- Good · 239 d · 69.5%
- Moderate · 97 d · 28.2%
- USG · 5 d · 1.5%
- Unhealthy · 3 d · 0.9%
How did Olmsted County's air break down in 2025?
Across 344 monitored days, 239 fell in the Good band (AQI 0–50) and 3 reached Unhealthy or worse. The worst single day peaked at AQI 166 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 344 days monitored. Median AQI: 39 (Good).
Insights: Olmsted County, Minnesota. EPA monitors recorded a median Air Quality Index of 39 across 344 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 239 (69%) fell in the Good band (AQI 0–50), 97 (28%) registered Moderate readings, and 5 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 65, while the worst single-day peak hit 166 (Unhealthy). Residents averaged about 20.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (230 days), Ozone (114 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -10.3 points (measured against 366 monitored days in 2020 and 344 in 2025, so raw day counts are not comparable) and the median AQI moved +1 points, placing the multi-year trajectory at worsening. The annual record contains 3 days at Unhealthy or worse. On those days, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Anoka (74.1% good, AQI 38); Becker (74.0% good, AQI 38); Beltrami (79.1% good, AQI 36); Blue Earth (65.3% good, AQI 42); Carlton (82.8% good, AQI 33); Cass (82.7% good, AQI 28).
Air Quality Summary
Good Days
69.5%
239 of 344 monitored days
-5.5pp vs 75% target
Max AQI Recorded
166
Unhealthy
Health Grade
Moderate
90th-pct AQI 65
Olmsted County, Good days share 69.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Olmsted County, Unhealthy-or-worse share 8.7%
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 344 monitored days across EPA AQI categories.
Good
239
69%
Moderate
97
28%
USG
5
1%
Unhealthy
3
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Olmsted County.
- PM2.5 · 230 days · 66.9%
- Ozone · 114 days · 33.1%
Health Impact Assessment
Moderate
Olmsted County's air quality is rated Moderate based on 69.5% good air days. There were 3 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 5 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 166. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 230 of 344 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Olmsted County. Highest Good-day share: 2020 (79.8%, 292 of 366 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 292 | 73 | 1 | 0 | 38 | 111 |
| 2021 | 275 | 84 | 2 | 0 | 39 | 125 |
| 2022 | 280 | 78 | 1 | 0 | 41 | 110 |
| 2023 | 189 | 161 | 14 | 1 | 49 | 167 |
| 2024 | 234 | 131 | 0 | 1 | 44 | 155 |
| 2025 | 239 | 97 | 5 | 3 | 39 | 166 |
How does Olmsted County compare?
How Olmsted County compares
Good-day share worse than typical
Olmsted County 69.5%
Aiken County, South Carolina 90.6%
Typical US county 76.0%
Median AQI about typical
Olmsted County 39
Aiken County, South Carolina 39
Typical US county 39
Unhealthy days / yr worse than typical
Olmsted County 3
Aiken County, South Carolina 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Olmsted County (39), not geographic neighbors.
Aiken County, South Carolina
Median AQI 39 · 90.6% Good-day share
Albany County, New York
Median AQI 39 · 68.5% Good-day share
Anderson County, Tennessee
Median AQI 39 · 94.3% Good-day share
Bay County, Michigan
Median AQI 39 · 70.4% Good-day share
Berkeley County, West Virginia
Median AQI 39 · 83.6% Good-day share
Boyd County, Kentucky
Median AQI 39 · 80.0% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Baker County, Florida
69.5% Good-day share · median AQI 44
Cabell County, West Virginia
69.5% Good-day share · median AQI 42
Trinity County, California
69.6% Good-day share · median AQI 31
Chelan County, Washington
69.6% Good-day share · median AQI 35
Pinellas County, Florida
69.6% Good-day share · median AQI 44
St. Clair County, Michigan
69.6% Good-day share · median AQI 39
Minnesota counties on the map
Geographic containment only, other monitored counties in Minnesota, independent of AQI or pollutant match.
What Olmsted County's air means for you
On most days the air here is fine, but PM2.5 drives 3 unhealthy-or-worse days a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 39 means for exposure. Health guidance
- See how Olmsted County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Olmsted County with its Minnesota neighbours before drawing a conclusion about the region. All of Minnesota
Based on 344 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Olmsted County, Minnesota? ▼
Olmsted County has a median Air Quality Index (AQI) of 39, rated "Good." 69.5% of monitored days (239 out of 344) had good air quality in 2025.
What is the main pollutant in Olmsted County? ▼
The primary pollutant in Olmsted County is Fine Particles (PM2.5), which was the main AQI driver on 230 days (67% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Olmsted County have? ▼
In 2025, Olmsted County recorded 3 unhealthy air days (3 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 166.
Is the air quality in Olmsted County getting better or worse? ▼
Air quality in Olmsted County is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 79.8% (292 of 366 days). Lowest qualifying Good-day share: 2023 at 51.8% (189 of 365 days).
What does AQI 39 mean for health? ▼
Olmsted County's median AQI of 39 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Olmsted County compare to other counties in Minnesota? ▼
Olmsted County has 69.5% good air days. Nearby counties in Minnesota: Anoka (74.1% good), Becker (74.0% good), Beltrami (79.1% good), Blue Earth (65.3% good), Carlton (82.8% good), Cass (82.7% good).
What is the 90th percentile AQI in Olmsted County? ▼
The 90th percentile AQI for Olmsted County is 65, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 166 (Unhealthy).
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Olmsted County, Minnesota · 2020–2025
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Every figure on PlainAirData 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.