Smoke: keep one room clean
Shut the windows and run an air purifier sized for the room.
Wildfire smoke guide →Air quality in Utah, county by county
14 Utah counties have enough EPA monitor data to count bad-air days. Weighted by population, they averaged about 16 days a year from 2021 to 2025 when the air was unhealthy for sensitive groups or worse.
CDC's model, which estimates every county from monitors and satellites, gives the average Utah county, weighted by population, about 4 smoky days (fine particles over 35.4 µg/m³, mostly wildfire smoke) and about 10 high-ozone days a year at its worst spot (2018 to 2022). See every county on the map.
Every Utah county with monitors
Most bad-air days first. 14 have a full report. Compare with the worst and the cleanest counties in the US.
| County | Bad-air days a year | |
|---|---|---|
| Salt Lake CountySalt Lake CityOzone | 30.2 | |
| Uintah CountyVernalOzone | 14.8 | |
| Davis CountyLaytonOzone | 14.2 | |
| Duchesne CountyOzone | 10.6 | |
| Weber CountyOgdenOzone | 7.2 | |
| Tooele CountyTooeleOzone | 7.0 | |
| Utah CountyProvoOzone and particles | 6.6 | |
| Cache CountyLoganWinter particles | 5.2 | |
| Carbon CountyPriceOzone and particles | 3.0 | |
| Box Elder CountyBrigham CityOzone and particles | 2.0 | |
| Iron CountyCedar CityOzone and particles | 1.2 | |
| San Juan CountyOzone | 1.2 | |
| Washington CountySt. GeorgeOzone | 1.0 | |
| Grand CountyOzone | 0.7 | |
| No Utah county with a monitor matches “”. Counties without a monitor aren't listed; a neighbor's numbers are a fair guide, or find it on the map. | ||
Counties without a monitor aren't listed. Air doesn't stop at the county line, so a neighbor's numbers are a fair guide.
What helps on a bad-air day
Check AirNow for today's reading and tomorrow's forecast, then match the step to the pollutant.
Upgrade the furnace filter
MERV 13 catches far more smoke than thin fiberglass filters.
Furnace filters →Questions people ask about air quality in Utah
Which county in Utah has the worst air?
Among Utah counties with EPA monitors, Salt Lake County had the most bad-air days from 2021 to 2025: about 30 bad-air days a year with an AQI over 100. That's about 1 day in 12.
How often is the air bad in Utah?
Weighted by population, Utah counties with monitors averaged about 16 bad-air days a year from 2021 to 2025 with an AQI over 100, when children, older adults and people with asthma should cut back outdoors. That's about 1 day in 23.
Which county in Utah has the cleanest air?
Of the 14 counties with enough monitor data, Grand County had the fewest: 0.7 a year from 2021 to 2025. Counties without monitors aren't ranked.
Where can I check today's air quality in Utah?
AirNow, run by the EPA and its partners, shows current readings and forecasts by ZIP code, and its fire and smoke map adds smoke plumes and low-cost sensors.
Sources: EPA AirData county AQI summaries, 2021 to 2025; CDC Environmental Public Health Tracking Network modeled PM2.5 and ozone, 2018 to 2022. Updated November 8, 2026.