Bad Air Days in Lincoln County, Montana: 8 a Year

8 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 125 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (100% particle days).

Which months to watch

Most bad days here fall in August and September. Averaged over 2016 to 2025.

Is a purifier worth it here?

Particles (wildfire smoke, dust) cause enough bad days here to matter. A HEPA purifier sized to your bedroom removes them; run it with windows shut on bad days.
Upgrade the furnace or AC filter to MERV 13 so the whole house is filtered, not just one room.

Better or worse than it was

In 2000 to 2009 this county averaged 8 bad days a year; in 2016 to 2025, 8. Not much has changed. The worst recent year was 2018, with 20 bad days on 365 monitored days.

Date	AQI	Main pollutant
2020-09-13	403	PM2.5
2020-09-14	347	PM2.5
2017-09-08	241	PM2.5
2020-09-15	226	PM2.5
2017-09-07	202	PM2.5

Most days, not the worst ones

Across 3,465 monitored days from 2016 to 2025, the air in Lincoln County rated Good on 46% of them, less often than the 72% typical of monitored counties, and Moderate on 51%. The median day sat at AQI 51; one day in ten went above 75.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)99%3,437 days
coarse dust (PM10)1%28 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	182	99	81	2	0	45	118
2024	365	185	178	2	0	49	116
2023	364	151	209	4	2	53	189
2022	365	184	175	6	2	49	174
2021	365	125	223	17	6	56	177
2020	366	175	182	9	7	52	403
2019	364	189	174	1	0	48	102
2018	365	139	206	20	12	55	186
2017	363	151	199	13	7	53	241
2016	366	212	154	0	0	44	99
2015	365	168	176	21	13	52	240
2014	365	209	154	2	0	41	133
2013	365	198	167	0	0	47	94
2012	364	180	184	0	0	51	96
2011	362	253	108	1	0	36	102
2010	365	171	190	4	0	52	107

*2025 may be a partial year in EPA's file.

Nearby counties on file

How this is counted

A bad air day is a day the county's daily AQI from EPA AirData went above 100, the level where EPA tells children, older adults and people with asthma or heart disease to cut back outdoors. Monitors do not run every day, so yearly counts are scaled to 365 days. This is the record, not today's air: for that, check AirNow. More on the method in how the county numbers are made, on the AQI 100 line in what counts as a bad air day.