Bonneville County, Idaho air quality history

Daily Air Quality Index summaries from EPA monitors in Bonneville, Idaho, 1989–2025.

93%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

359

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Bonneville, Idaho on 359 days. 334 of those days (93%) were in the Good range, and the median daily AQI was 22. That median is lower than the typical monitored county in Idaho (median 35 across 18 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 359 days. Across the years with fuller monitoring, the share of Good days rose: an average of 81% in 2001–2005 versus 91% in 2023–2025.

Years with fewer than 120 monitored days (1999, 2000, 2003, 2004, 2008, 2015…) 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)	359	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	359	334	25	0	0	22	43	95	PM2.5
2024	364	316	48	0	0	22	54	91	PM2.5
2023	348	326	22	0	0	25	44	84	PM2.5
2022	357	306	50	1	0	27	53	109	PM2.5
2021	356	275	72	9	0	31	67	144	PM2.5
2020	362	298	59	1	4	28	56	155	PM2.5
2019	357	287	70	0	0	38	53	67	PM2.5
2018	352	268	81	2	1	36	61	154	PM2.5
2017	358	277	77	4	0	32	56	149	PM2.5
2016	324	252	72	0	0	35	55	69	PM2.5
2015	104	92	12	0	0	23	51	63	PM2.5
2008	114	99	15	0	0	28	53	64	PM2.5
2007	276	197	79	0	0	34	58	84	PM2.5
2006	274	250	24	0	0	29	47	68	PM2.5
2005	318	310	8	0	0	27	38	81	PM2.5
2004	55	36	17	1	1	34	72	153	PM2.5
2003	116	100	16	0	0	29	55	70	PM2.5
2002	132	88	44	0	0	36	63	81	PM2.5
2001	120	94	26	0	0	33	68	82	PM2.5
2000	66	48	18	0	0	35	65	89	PM2.5
1999	57	47	9	1	0	29	58	115	PM2.5
1998	62	59	3	0	0	21	41	88	PM10
1997	60	58	2	0	0	23	41	63	PM10
1996	61	55	6	0	0	20	47	73	PM10
1995	62	61	1	0	0	20	36	56	PM10
1994	10	10	0	0	0	21	36	36	PM10
1993	47	42	5	0	0	29	51	63	PM10
1992	53	49	4	0	0	29	45	96	PM10
1991	41	41	0	0	0	28	46	49	PM10
1990	56	55	1	0	0	22	37	57	PM10
1989	59	52	7	0	0	23	52	69	PM10

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 Idaho with a similar median AQI in 2025

All monitored counties in Idaho

Source: U.S. EPA AirData, “Annual AQI by County” files for 1989–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem