Williston, North Dakota Air Quality
Williston has a median AQI of 34, earning an air quality grade of A — excellent air quality that ranks better than 83% of US cities. Air quality has remained relatively stable over the past decade. Ground-level ozone is the primary concern, typically peaking on warm sunny days due to vehicle and industrial emissions. In 2019, Williston recorded 324 good air quality days (90% of monitored days).
Population: 28,056 • County: Williams
Current AQI
Quick Facts
| Current AQI | 8 — Good |
| Air Quality Grade | A |
| Median AQI (2019) | 34 |
| vs. U.S. Cities | Better than 83% |
| Primary Pollutant | Ozone |
| Unhealthy Days/Year | 0 |
| 10-Year Trend | → Stable |
| 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 Williston is sourced from the TRNP-NU monitoring area, located approximately 44 miles from city center. This EPA-certified station continuously tracks ground-level ozone, the primary driver of air quality alerts in this area.
Williston 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
Williston Median AQI by Year
Annual EPA air quality data for Williston — median AQI, day-category breakdown, and primary pollutant per year.
| Year | Median AQI | Good Days | Unhealthy Days | Max AQI | Primary Pollutant |
|---|---|---|---|---|---|
| 2019 | 34 | 324 | — | 77 | Ozone |
| 2018 | 38 | 291 | — | 100 | Ozone |
| 2017 | 37 | 302 | 2 | 131 | Ozone |
| 2016 | 32 | 349 | — | 94 | Ozone |
Source: EPA Air Quality System (AQS) annual summaries. "Unhealthy Days" includes Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous categories.
2019 Air Quality Summary
Primary Pollutant Days (2019)
Days when each pollutant was the primary driver of AQI. Learn about pollutants →
Frequently Asked Questions About Williston Air Quality
What is the air quality in Williston today?
The current AQI in Williston is 8, 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 Williston getting better or worse?
Air quality in Williston has been stable. The median AQI has risen 2 points (from 32 in 2016 to 34 in 2019).
What is the most common air pollutant in Williston?
Ozone is the primary air pollutant in Williston, responsible for 263 days (73% of monitored days) in 2019. 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 Williston have per year?
In 2019, Williston recorded 90% good air quality days (324 days) out of 362 monitored days. There were 0 Unhealthy for Sensitive Groups days and 0 Unhealthy days (AQI above 100). The highest single-day AQI recorded was 77.
What air quality grade does Williston receive?
Williston receives an air quality grade of A, placing it better than 83% of US cities. This is based on a median AQI of 34 in 2019, with 324 good air quality days. The EPA monitors air quality in this area continuously using certified monitoring stations.
Air Quality Grade
Better than 83% of US cities
Nearby Cities
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National Rankings
See how Williston compares to every other US city by air quality.
Best Air Quality Cities →All city rankingsRecommended Air Purifiers for Williston
Ozone is Williston'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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Other Great Options
Molekule Air Pro
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Honeywell HPA300
Powerful workhorse for large rooms. Built to last.
RabbitAir MinusA2
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