Roosevelt County, Montana air quality history

Daily Air Quality Index summaries from EPA monitors in Roosevelt, Montana, 1992–2025.

87%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Roosevelt, Montana on 94 days. 82 of those days (87%) were in the Good range, and the median daily AQI was 16. That median is lower than the typical monitored county in Montana (median 25.5 across 18 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 94 days.

EPA did not report an AQI for every day of 2025 here (94 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (2020, 2021, 2022, 2023, 2024, 2025…) 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)	94	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	94	82	11	0	1	16	54	196	PM2.5
2024	98	87	10	1	0	13	52	109	PM2.5
2023	72	62	9	0	1	13	52	161	PM2.5
2022	101	98	3	0	0	14	30	64	PM2.5
2021	100	89	11	0	0	16	56	99	PM2.5
2020	77	74	3	0	0	12	34	60	PM2.5
2019	93	89	4	0	0	13	29	54	PM2.5
2018	105	93	10	2	0	17	52	134	PM2.5
2017	90	85	5	0	0	15	40	76	PM2.5
2016	104	100	4	0	0	13	25	80	PM2.5
2015	102	95	3	3	1	14	43	153	PM2.5
2014	109	105	4	0	0	15	36	74	PM2.5
2013	106	103	3	0	0	17	37	58	PM2.5
2012	103	99	4	0	0	18	38	54	PM2.5
2011	103	99	4	0	0	17	38	64	PM2.5
2010	97	90	7	0	0	20	47	75	PM2.5
2009	102	101	1	0	0	17	32	52	PM2.5
2008	118	113	5	0	0	19	41	69	PM2.5
2007	116	108	8	0	0	19	44	82	PM2.5
2006	115	109	6	0	0	18	40	78	PM2.5
2005	115	115	0	0	0	16	33	49	PM2.5
2004	110	103	7	0	0	16	42	78	PM2.5
2003	119	114	5	0	0	18	35	57	PM2.5
2002	76	72	4	0	0	18	40	57	PM2.5
2001	56	55	1	0	0	11	32	54	PM10
2000	52	51	1	0	0	13	35	54	PM10
1999	41	40	1	0	0	14	40	57	PM10
1998	52	42	10	0	0	24	58	90	PM10
1997	38	35	3	0	0	17	46	60	PM10
1996	53	52	1	0	0	17	35	76	PM10
1995	38	38	0	0	0	14	24	37	PM10
1994	52	52	0	0	0	14	23	33	PM10
1993	47	47	0	0	0	15	22	27	PM10
1992	13	13	0	0	0	12	27	44	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 Montana with a similar median AQI in 2025

All monitored counties in Montana

Source: U.S. EPA AirData, “Annual AQI by County” files for 1992–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem