Knife River, Minnesota Air Quality
Knife River has a median AQI of 34, earning an air quality grade of A — excellent air quality that ranks better than 84% of US cities. Air quality has been trending worse over the past decade, a concern for local residents and health officials. Ground-level ozone is the primary concern, typically peaking on warm sunny days due to vehicle and industrial emissions. In 2025, Knife River recorded 155 good air quality days (96% of monitored days) and 3 unhealthy days.
Population: 131 • County: Lake
Current AQI
Quick Facts
| Current AQI | 10 — Good |
| Air Quality Grade | A |
| Median AQI (2025) | 34 |
| vs. U.S. Cities | Better than 84% |
| Primary Pollutant | Ozone |
| Unhealthy Days/Year | 3 |
| 10-Year Trend | ↓ Worsening |
| Data Source | EPA AQS (historical) · AirNow (live) |
Health Recommendation
Air quality is satisfactory, and air pollution poses little or no risk.
It's a great day to be active outside!
5-Day AQI Forecast
Last 90 Days
Current Pollutant Levels
Real-time data from EPA AirNow
Local Air Quality Context
Air quality data for Knife River is sourced from the Duluth-WDSE monitoring area, located approximately 17 miles from city center. This EPA-certified station continuously tracks ground-level ozone, the primary driver of air quality alerts in this area.
Knife River has relatively consistent air quality throughout the year without a strong seasonal peak. Air quality is primarily influenced by local traffic, industrial activity, and regional weather patterns rather than a single seasonal driver.
AQI Trend (10 Years)
Air Quality Days by Year
Knife River Median AQI by Year
Annual EPA air quality data for Knife River — median AQI, day-category breakdown, and primary pollutant per year.
| Year | Median AQI | Good Days | Unhealthy Days | Max AQI | Primary Pollutant |
|---|---|---|---|---|---|
| 2025 | 34 | 155 | 3 | 129 | Ozone |
| 2024 | 32 | 330 | 1 | 110 | PM2.5 |
| 2023 | 36 | 282 | 2 | 114 | PM2.5 |
| 2022 | 31 | 342 | — | 78 | Ozone |
| 2021 | 31 | 315 | 4 | 160 | Ozone |
| 2020 | 34 | 344 | — | 71 | PM2.5 |
| 2019 | 31 | 333 | — | 83 | PM2.5 |
| 2018 | 34 | 310 | — | 96 | Ozone |
| 2017 | 30 | 330 | — | 85 | Ozone |
| 2016 | 24 | 347 | — | 86 | Ozone |
Source: EPA Air Quality System (AQS) annual summaries. "Unhealthy Days" includes Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous categories.
2025 Air Quality Summary
Primary Pollutant Days (2025)
Days when each pollutant was the primary driver of AQI. Learn about pollutants →
Frequently Asked Questions About Knife River Air Quality
What is the air quality in Knife River today?
The current AQI in Knife River is 10, rated "Good". Air quality is good — outdoor activity is safe for everyone today. Air quality is satisfactory, and air pollution poses little or no risk.
Is air quality in Knife River getting better or worse?
Air quality in Knife River has been worsening. The median AQI has risen 10 points (from 24 in 2016 to 34 in 2025), a concern for local health officials.
What is the most common air pollutant in Knife River?
Ozone is the primary air pollutant in Knife River, responsible for 98 days (60% of monitored days) in 2025. Ground-level ozone forms when sunlight reacts with emissions from vehicles and industry, typically peaking on hot summer afternoons.
How many unhealthy air days does Knife River have per year?
In 2025, Knife River recorded 96% good air quality days (155 days) out of 162 monitored days. There were 3 Unhealthy for Sensitive Groups days and 0 Unhealthy days (AQI above 100). The highest single-day AQI recorded was 129.
What air quality grade does Knife River receive?
Knife River receives an air quality grade of A, placing it better than 84% of US cities. This is based on a median AQI of 34 in 2025, with 155 good air quality days. The EPA monitors air quality in this area continuously using certified monitoring stations.
Air Quality Grade
Better than 84% of US cities
Nearby Cities
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National Rankings
See how Knife River compares to every other US city by air quality.
Best Air Quality Cities →All city rankingsRecommended Air Purifiers for Knife River
Ozone is Knife River's primary pollutant. Standard HEPA filters don't capture ozone molecules — you need activated carbon or PECO technology to chemically break them down. We highlight those units here.
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