Median AQI
22
Good
California · County air quality · 2025
Mono County, California
Median AQI 22 (Good). 92.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 22
- Median AQI
- 92.8%
- Good-air days
- 0
- Unhealthy days
- 82%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Mono County's air is good on balance, cleaner than most US counties, a median AQI of 22 with 92.8% of 181 monitored days in the Good band, driven mainly by PM2.5.
- 22
- median AQI · Good
- 92.8%
- days rated Good
- PM2.5
- main pollutant
- 82%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 104.
Data updated July 2026
- Good · 168 d · 92.8%
- Moderate · 12 d · 6.6%
- USG · 1 d · 0.6%
How did Mono County's air break down in 2025?
Across 181 monitored days, 168 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 104 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 22 (Good).
Insights: Mono County, California. EPA monitors recorded a median Air Quality Index of 22 across 181 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 168 (93%) fell in the Good band (AQI 0–50), 12 (7%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 44, while the worst single-day peak hit 104 (USG). Residents averaged about 27.8 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (94 days), PM10 (87 days). Across the 2020–2025 trend window, good days shifted by -15 and the median AQI moved -29 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 104, usg but never Unhealthy. Nearby counties show comparable readings: Amador (84.8% good, AQI 40); Butte (66.1% good, AQI 47); Calaveras (73.9% good, AQI 43); Colusa (84.9% good, AQI 39); Del Norte (81.0% good, AQI 33); El Dorado (85.8% good, AQI 39).
Air Quality Summary
Good Days
92.8%
168 of 181 monitored days
17.8pp vs 75% target
Max AQI Recorded
104
USG
Health Grade
Excellent
90th-pct AQI 44
Mono County, Good days share 92.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Mono County, Unhealthy-or-worse share 0.0%
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 181 monitored days across EPA AQI categories.
Good
168
93%
Moderate
12
7%
USG
1
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Mono County.
- PM2.5 · 94 days · 51.9%
- PM10 · 87 days · 48.1%
Health Impact Assessment
Excellent
Mono County's air quality is rated Excellent based on 92.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 92.8% of monitored days in 2025, with a median AQI of 22. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 94 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Mono County. Best year: 2024 (341 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 183 | 117 | 13 | 14 | 51 | 2088 |
| 2021 | 260 | 78 | 12 | 11 | 27 | 2971 |
| 2022 | 276 | 61 | 5 | 7 | 27 | 8368 |
| 2023 | 325 | 35 | 1 | 1 | 24 | 1829 |
| 2024 | 341 | 25 | 0 | 0 | 19 | 69 |
| 2025 | 168 | 12 | 1 | 0 | 22 | 104 |
How does Mono County compare?
How Mono County compares
Good-day share better than US avg
Mono County 92.8%
Amador County, California 84.8%
US average 76.5%
Median AQI better than US avg
Mono County 22
Amador County, California 40
US average 38
Unhealthy days / yr about average
Mono County 0
Amador County, California 0
US average 0
Other Counties in California
Air quality comparison for nearby counties in California.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Mono County.
Blaine County, Idaho
AQI 22 · 99.4% good
Cass County, Minnesota
AQI 22 · 94.4% good
Chase County, Kansas
AQI 22 · 88.9% good
Deschutes County, Oregon
AQI 22 · 93.4% good
Douglas County, Nevada
AQI 22 · 90.9% good
Franklin County, Idaho
AQI 22 · 95.8% good
What Mono County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 22 means for exposure. Health guidance
- See how Mono County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Mono County with its California neighbours before drawing a conclusion about the region. All of California
Based on 181 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 Mono County, California? ▼
Mono County has a median Air Quality Index (AQI) of 22, rated "Good." 92.8% of monitored days (168 out of 181) had good air quality in 2025.
What is the main pollutant in Mono County? ▼
The primary pollutant in Mono County is Fine Particles (PM2.5), which was the main AQI driver on 94 days (52% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Mono County have? ▼
In 2025, Mono County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 104.
Is the air quality in Mono County getting better or worse? ▼
Air quality in Mono County is improving based on 5-year trends (2020-2025). Best year: 2024 with 341 good days. Worst year: 2025 with 168 good days.
What does AQI 22 mean for health? ▼
Mono County's median AQI of 22 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Mono County compare to other counties in California? ▼
Mono County has 92.8% good air days. Nearby counties in California: Amador (84.8% good), Butte (66.1% good), Calaveras (73.9% good), Colusa (84.9% good), Del Norte (81.0% good), El Dorado (85.8% good).
What is the 90th percentile AQI in Mono County? ▼
The 90th percentile AQI for Mono County is 44, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 104 (USG).
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.