Median AQI
16
Good
Minnesota · County air quality · 2025
Cook County, Minnesota
Median AQI 16 (Good). 88.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 16
- Median AQI
- 88.0%
- Good-air days
- 8
- Unhealthy days
- 76%
- Cleaner than US counties
Cook County's 2025 annual median AQI is 16 (Good), with 88.0% Good days
According to the U.S. EPA Air Quality System, Cook County, Minnesota posted a 2025 median AQI of 16 (Good) across 358 monitored days, with 88.0% rated Good and 8 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Cook County's 88.0% Good-day share places it cleaner than 76% of US counties in 2025.
- Closest median-AQI peer
- Pacific County (99.7% Good, median AQI 16) is the closest nationwide median-AQI peer to Cook County.
- 2020–2025 trend
- Cook County's floor-qualifying Good-day share is worsening from 2020 to 2025 (98.6% → 88.2%).
- Median AQI
- Median AQI: 16
The verdict
According to EPA Air Quality System monitoring data, Cook County's air is good on balance, cleaner than most US counties, a median AQI of 16 with 88.0% of 358 monitored days in the Good band, driven mainly by PM2.5.
- 16
- median AQI · Good
- 88.0%
- days rated Good
- PM2.5
- main pollutant
- 76%
- cleaner than US counties
8 days reached Unhealthy or worse; the worst single reading hit AQI 201.
Annual release change
What changed in the 2025 EPA annual release
- Cook County's Unhealthy-category days rose from 0 to 7 between the 2024 and 2025 EPA annual releases, a change of +7 days.
- Cook County's peak single-day AQI rose from 138 to 201 between the 2024 and 2025 EPA annual releases, a change of +63 points.
- Cook County's Good-day share fell from 92.2% to 88.0% between the 2024 and 2025 EPA annual releases, a change of -4.3 percentage points.
Data updated August 2026
- Good · 315 d · 88.0%
- Moderate · 31 d · 8.7%
- USG · 4 d · 1.1%
- Unhealthy · 7 d · 2.0%
- Very Unhealthy · 1 d · 0.3%
How did Cook County's air break down in 2025?
Across 358 monitored days, 315 fell in the Good band (AQI 0–50) and 8 reached Unhealthy or worse. The worst single day peaked at AQI 201 (Very Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 358 days monitored. Median AQI: 16 (Good).
Insights: Cook County, Minnesota. EPA monitors recorded a median Air Quality Index of 16 across 358 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 315 (88%) fell in the Good band (AQI 0–50), 31 (9%) registered Moderate readings, and 4 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 201 (Very Unhealthy). Residents averaged about 26.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (358 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -10.6 points and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The annual record contains 8 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
88.0%
315 of 358 monitored days
13.0pp vs 75% target
Max AQI Recorded
201
Very Unhealthy
Health Grade
Good
90th-pct AQI 54
Cook County, Good days share 88.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Cook County, Unhealthy-or-worse share 22.3%
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 358 monitored days across EPA AQI categories.
Good
315
88%
Moderate
31
9%
USG
4
1%
Unhealthy
7
2%
Very Unhealthy
1
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Cook County.
- PM2.5 · 358 days · 100.0%
Health Impact Assessment
Good
Cook County's air quality is rated Good based on 88.0% good air days. There were 8 unhealthy days in 2025 when outdoor activity should be limited.
Air quality reached unhealthy levels on 8 days in 2025 (7 Unhealthy, 1 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is PM2.5, driving AQI on 358 of 358 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Cook County. Highest Good-day share: 2022 (99.1%, 327 of 330 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 340 | 5 | 0 | 0 | 13 | 59 |
| 2021 | 306 | 18 | 3 | 1 | 9 | 153 |
| 2022 | 327 | 3 | 0 | 0 | 4 | 54 |
| 2023 | 298 | 47 | 1 | 0 | 13 | 120 |
| 2024 | 333 | 25 | 3 | 0 | 16 | 138 |
| 2025 | 315 | 31 | 4 | 7 | 16 | 201 |
How does Cook County compare?
How Cook County compares
Good-day share better than typical
Cook County 88.0%
Pacific County, Washington 99.7%
Typical US county 76.0%
Median AQI better than typical
Cook County 16
Pacific County, Washington 16
Typical US county 39
Unhealthy days / yr worse than typical
Cook County 8
Pacific County, Washington 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Cook County (16), not geographic neighbors.
Pacific County, Washington
Median AQI 16 · 99.7% Good-day share
Potter County, Texas
Median AQI 16 · 94.1% Good-day share
Sanders County, Montana
Median AQI 16 · 82.0% Good-day share
Taos County, New Mexico
Median AQI 16 · 98.9% Good-day share
Blaine County, Idaho
Median AQI 17 · 96.6% Good-day share
Luna County, New Mexico
Median AQI 17 · 84.7% 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).
Pitt County, North Carolina
88.0% Good-day share · median AQI 37
Pike County, Kentucky
88.2% Good-day share · median AQI 34
Clackamas County, Oregon
87.6% Good-day share · median AQI 31
Susquehanna County, Pennsylvania
88.4% Good-day share · median AQI 22
Roane County, Tennessee
88.6% Good-day share · median AQI 29
Alachua County, Florida
88.7% Good-day share · median AQI 37
Minnesota counties on the map
Geographic containment only, other monitored counties in Minnesota, independent of AQI or pollutant match.
What Cook County's air means for you
On most days the air here is fine, but PM2.5 drives 8 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 16 means for exposure. Health guidance
- See how Cook County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Cook County with its Minnesota neighbours before drawing a conclusion about the region. All of Minnesota
Based on 358 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 Cook County, Minnesota? ▼
Cook County has a median Air Quality Index (AQI) of 16, rated "Good." 88.0% of monitored days (315 out of 358) had good air quality in 2025.
What is the main pollutant in Cook County? ▼
The primary pollutant in Cook County is Fine Particles (PM2.5), which was the main AQI driver on 358 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Cook County have? ▼
In 2025, Cook County recorded 8 unhealthy air days (7 Unhealthy, 1 Very Unhealthy, 0 Hazardous). The maximum AQI reached 201.
Is the air quality in Cook County getting better or worse? ▼
Air quality in Cook 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: 2022 at 99.1% (327 of 330 days). Lowest qualifying Good-day share: 2023 at 86.1% (298 of 346 days).
What does AQI 16 mean for health? ▼
Cook County's median AQI of 16 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Cook County compare to other counties in Minnesota? ▼
Cook County has 88.0% 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 Cook County? ▼
The 90th percentile AQI for Cook County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 201 (Very 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 Cook 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.