Mono County, California air quality history

Daily Air Quality Index summaries from EPA monitors in Mono, California, 1980–2025.

90%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

365

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Mono, California on 365 days. 329 of those days (90%) were in the Good range, and the median daily AQI was 21. That median is lower than the typical monitored county in California (median 45.5 across 46 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 196 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 89% in 1980–1982 versus 91% in 2023–2025.

Years with fewer than 120 monitored days (1999) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Fine particles (PM2.5)	196	54%
Coarse particles (PM10)	169	46%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Very Unhealthy	Hazardous	Median AQI	90th pct.	Max AQI	Main pollutant
2025	365	329	29	3	2	1	1	21	50	704	PM2.5
2024	366	341	25	0	0	0	0	19	45	69	PM2.5
2023	365	325	35	1	1	0	3	24	51	1829	PM2.5
2022	365	276	61	5	7	1	15	27	68	8368	PM2.5
2021	364	260	78	12	11	0	3	27	84	2971	PM2.5
2020	366	183	117	13	14	11	28	51	224	2088	PM2.5
2019	365	242	108	6	0	0	9	34	83	4227	PM2.5
2018	365	252	84	14	10	3	2	27	85	1049	PM2.5
2017	365	300	40	5	1	4	15	18	63	3767	PM10
2016	366	312	21	3	6	0	24	18	63	7063	PM10
2015	365	318	28	2	4	1	12	15	54	4384	PM10
2014	365	332	21	1	3	2	6	16	45	2739	PM10
2013	365	311	43	6	1	0	4	19	58	3479	PM10
2012	366	326	16	5	5	0	14	18	54	4244	PM10
2011	365	313	34	4	1	0	13	18	57	5260	PM10
2010	365	308	35	4	5	1	12	18	61	4658	PM10
2009	365	317	32	4	2	1	9	18	58	15556	PM10
2008	296	241	40	3	3	1	8	21	64	2907	PM10
2007	276	239	23	1	2	1	10	18	66	10968	PM10
2006	269	237	16	6	2	0	8	16	55	4609	PM10
2005	250	209	27	1	4	1	8	20	68	2172	PM10
2004	331	196	104	23	1	0	7	48	100	926	Ozone
2003	314	175	119	11	2	1	6	49	90	6215	Ozone
2002	299	260	31	2	0	1	5	23	56	7060	PM10
2001	359	248	91	16	2	1	1	39	93	4811	Ozone
2000	349	324	16	1	0	1	7	11	31	11464	PM10
1999	117	116	1	0	0	0	0	11	24	90	PM10
1998	265	225	38	2	0	0	0	20	61	108	CO
1997	365	276	77	12	0	0	0	38	77	126	Ozone
1996	356	259	79	17	1	0	0	42	87	161	Ozone
1995	365	282	76	5	2	0	0	42	71	190	Ozone
1994	365	252	89	21	3	0	0	44	90	166	Ozone
1993	365	242	105	16	0	0	2	46	87	919	Ozone
1992	295	188	74	24	8	0	1	44	105	377	Ozone
1991	271	198	70	3	0	0	0	35	77	108	Ozone
1990	283	188	75	18	2	0	0	45	93	164	Ozone
1989	267	211	49	7	0	0	0	37	67	122	Ozone
1988	366	226	103	33	4	0	0	46	101	182	Ozone
1987	365	219	106	39	1	0	0	46	101	164	Ozone
1986	365	200	115	38	12	0	0	47	119	169	Ozone
1985	365	271	80	12	2	0	0	40	77	161	Ozone
1984	250	169	65	14	2	0	0	42	90	154	Ozone
1983	284	212	54	17	1	0	0	37	87	154	Ozone
1982	306	260	41	5	0	0	0	34	59	140	CO
1981	284	276	8	0	0	0	0	11	35	70	CO
1980	205	172	33	0	0	0	0	24	56	91	CO

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in California with a similar median AQI in 2025

All monitored counties in California

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem