California · County air quality · 2025
Mono County, California
Median AQI 21 (Good). 90.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 21
- Median AQI
- 90.1%
- Good-air days
- 4
- Unhealthy days
- 80%
- Cleaner than US counties
Mono County's 2025 annual median AQI is 21 (Good), with 90.1% Good days
According to the U.S. EPA Air Quality System, Mono County, California posted a 2025 median AQI of 21 (Good) across 365 monitored days, with 90.1% rated Good and 4 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Mono County's 90.1% Good-day share places it cleaner than 80% of US counties in 2025.
- Closest median-AQI peer
- Adams County (90.5% Good, median AQI 21) is the closest nationwide median-AQI peer to Mono County.
- 2020–2025 trend
- Mono County's floor-qualifying Good-day share is improving from 2020 to 2025 (56.0% → 90.6%).
- Median AQI
- Median AQI: 21
According to the 2025 EPA AQS county release on PlainAirData, Mono County, California ranks #38 of 951 by median AQI (21) and #192 by good-day share (90.1%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Mono County's peak single-day AQI rose from 69 to 704 between the 2024 and 2025 EPA annual releases, a change of +635 points.
- Mono County's Good-day share fell from 93.2% to 90.1% between the 2024 and 2025 EPA annual releases, a change of -3.0 percentage points.
- Mono County's Unhealthy-category days rose from 0 to 2 between the 2024 and 2025 EPA annual releases, a change of +2 days.
Data updated August 2026
- Good · 329 d · 90.1%
- Moderate · 29 d · 7.9%
- USG · 3 d · 0.8%
- Unhealthy · 2 d · 0.5%
- Very Unhealthy · 1 d · 0.3%
- Hazardous · 1 d · 0.3%
How did Mono County's air break down in 2025?
Across 365 monitored days, 329 fell in the Good band (AQI 0–50) and 4 reached Unhealthy or worse. The worst single day peaked at AQI 704 (Hazardous) - a reading beyond the EPA’s standard 0–500 AQI scale, reflecting an extreme wildfire-smoke event or a transient monitor anomaly.
EPA AQS →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Mono County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Mono County's Good-day share is 90.1% - cleaner than 80% of that comparison set.
Mono County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
90.1% Cleaner than 80% higher than 80% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Mono County.
- PM2.5 · 196 days · 53.7%
- PM10 · 169 days · 46.3%
2024 daily-monitor rhythm in Mono County
Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Jul posted the highest typical readings (median AQI 34, peak 52); Nov was cleanest at median 13. Summer months (Jun–Aug) averaged median AQI 28 vs 16 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,826 daily readings show a recurring local pattern: Sep has the highest matched-month median AQI (87), while Mar is lowest (19). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Mono County's air quality is rated Excellent based on 90.1% good air days. There were 4 unhealthy days in 2025 when outdoor activity should be limited.
Air quality posed significant health risk in 2025. Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, pregnant women, and adults over 65, should monitor AirNow.gov alerts and limit outdoor activity on Unhealthy (AQI 151+) and Very Unhealthy (201+) days. Peak readings reached AQI 704, beyond EPA's standard 0-500 scale, indicating an extreme event.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
Note: EPA's standard AQI scale caps at 500 (Hazardous category 301-500). The 704 peak reading represents an extreme event, typically wildfire smoke, extrapolated beyond the index's design range. See EPA wildfire smoke guidance.
The dominant pollutant is PM2.5, driving AQI on 196 of 365 monitored days.
5-Year Air Quality Trend
Air quality is improving in Mono County. Highest Good-day share: 2024 (93.2%, 341 of 366 monitored 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 | 329 | 29 | 3 | 2 | 21 | 704 |
How does Mono County compare?
How Mono County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Mono County, California · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.