Median AQI
54
Moderate
Utah · County air quality · 2025
Salt Lake County, Utah
Median AQI 54 (Moderate). 37.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 54
- Median AQI
- 37.0%
- Good-air days
- 1
- Unhealthy days
- 2%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Salt Lake County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 54 with 37.0% of 305 monitored days in the Good band, driven mainly by Ozone.
- 54
- median AQI · Moderate
- 37.0%
- days rated Good
- Ozone
- main pollutant
- 2%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 175.
Data updated July 2026
- Good · 113 d · 37.0%
- Moderate · 177 d · 58.0%
- USG · 14 d · 4.6%
- Unhealthy · 1 d · 0.3%
How did Salt Lake County's air break down in 2025?
Across 305 monitored days, 113 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 175 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 305 days monitored. Median AQI: 54 (Moderate).
Insights: Salt Lake County, Utah. EPA monitors recorded a median Air Quality Index of 54 across 305 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 113 (37%) fell in the Good band (AQI 0–50), 177 (58%) registered Moderate readings, and 14 (5%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 90, while the worst single-day peak hit 175 (Unhealthy). Residents averaged about 11.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (204 days), PM2.5 (83 days), PM10 (11 days), NO2 (6 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -30 and the median AQI moved +0 points, placing the multi-year trajectory at stable. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Box Elder (60.0% good, AQI 48); Cache (61.2% good, AQI 46); Carbon (62.9% good, AQI 47); Davis (59.5% good, AQI 48); Duchesne (59.4% good, AQI 47); Garfield (100.0% good, AQI 4).
Air Quality Summary
Good Days
37.0%
113 of 305 monitored days
-38.0pp vs 75% target
Max AQI Recorded
175
Unhealthy
Health Grade
Poor
90th-pct AQI 90
Salt Lake County, Good days share 37.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Salt Lake County, Unhealthy-or-worse share 0.3%
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 305 monitored days across EPA AQI categories.
Good
113
37%
Moderate
177
58%
USG
14
5%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Salt Lake County.
- Ozone · 204 days · 66.9%
- PM2.5 · 83 days · 27.2%
- PM10 · 11 days · 3.6%
- NO₂ · 6 days · 2.0%
- CO · 1 days · 0.3%
Health Impact Assessment
Poor
Salt Lake County's air quality is rated Poor based on 37.0% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 14 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 175. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 204 of 305 monitored days.
5-Year Air Quality Trend
Air quality is stable in Salt Lake County. Best year: 2024 (150 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 143 | 200 | 21 | 1 | 54 | 214 |
| 2021 | 122 | 195 | 39 | 9 | 59 | 177 |
| 2022 | 101 | 236 | 28 | 0 | 60 | 147 |
| 2023 | 149 | 200 | 15 | 1 | 54 | 154 |
| 2024 | 150 | 173 | 38 | 4 | 54 | 230 |
| 2025 | 113 | 177 | 14 | 1 | 54 | 175 |
How does Salt Lake County compare?
How Salt Lake County compares
Good-day share worse than US avg
Salt Lake County 37.0%
Box Elder County, Utah 60.0%
US average 76.5%
Median AQI worse than US avg
Salt Lake County 54
Box Elder County, Utah 48
US average 38
Unhealthy days / yr worse than US avg
Salt Lake County 1
Box Elder County, Utah 0
US average 0
Other Counties in Utah
Air quality comparison for nearby counties in Utah.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Salt Lake County.
Denver County, Colorado
AQI 54 · 44.2% good
Franklin County, Ohio
AQI 54 · 39.8% good
Fresno County, California
AQI 54 · 40.1% good
Hamilton County, Ohio
AQI 54 · 32.1% good
Hidalgo County, Texas
AQI 54 · 36.2% good
Inyo County, California
AQI 54 · 40.7% good
What Salt Lake County's air means for you
On most days the air here is fine, but Ozone drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 54 means for exposure. Health guidance
- See how Salt Lake County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Salt Lake County with its Utah neighbours before drawing a conclusion about the region. All of Utah
Based on 305 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Salt Lake County, Utah? ▼
Salt Lake County has a median Air Quality Index (AQI) of 54, rated "Moderate." 37.0% of monitored days (113 out of 305) had good air quality in 2025.
What is the main pollutant in Salt Lake County? ▼
The primary pollutant in Salt Lake County is Ozone (O3), which was the main AQI driver on 204 days (67% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Salt Lake County have? ▼
In 2025, Salt Lake County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 175.
Is the air quality in Salt Lake County getting better or worse? ▼
Air quality in Salt Lake County is stable based on 5-year trends (2020-2025). Best year: 2024 with 150 good days. Worst year: 2022 with 101 good days.
What does AQI 54 mean for health? ▼
Salt Lake County's median AQI of 54 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Salt Lake County compare to other counties in Utah? ▼
Salt Lake County has 37.0% good air days. Nearby counties in Utah: Box Elder (60.0% good), Cache (61.2% good), Carbon (62.9% good), Davis (59.5% good), Duchesne (59.4% good), Garfield (100.0% good).
What is the 90th percentile AQI in Salt Lake County? ▼
The 90th percentile AQI for Salt Lake County is 90, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 175 (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.
Every figure on PlainAir 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.