Bad Air Days in Dunn County, North Dakota: 5 a Year

5 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 237 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (93% particle days).

Which months to watch

Most bad days here fall in September and July and August and May and June. 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 0 bad days a year; in 2016 to 2025, 5. It has got worse. The worst recent year was 2023, with 17 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-05-17	318	PM2.5
2025-05-31	217	PM2.5
2025-06-11	190	PM2.5
2021-08-16	184	PM2.5
2025-08-10	177	PM2.5

An ordinary day in Dunn

Across 3,598 monitored days from 2016 to 2025, the air in Dunn County rated Good on 85% of them, more often than the 72% typical of monitored counties, and Moderate on 14%. The median day sat at AQI 37; one day in ten went above 56.

The pollutant setting the AQI on an ordinary day here:

ozone71%2,567 days
fine particles (PM2.5)28%1,018 days

Dunn County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	291	65	9	3	39	217
2024	365	304	53	8	3	37	157
2023	365	263	85	17	6	41	318
2022	362	308	54	0	0	37	82
2021	365	277	78	10	3	39	184
2020	366	347	19	0	0	34	62
2019	365	343	22	0	0	35	87
2018	349	297	52	0	0	35	90
2017	330	288	40	2	1	37	157
2016	366	345	21	0	0	35	90
2015	365	295	59	11	1	38	153
2014	362	332	29	1	0	35	103
2013	363	327	36	0	0	35	67
2012	365	300	65	0	0	39	75
2011	290	278	12	0	0	33	71
2010	112	102	10	0	0	41	87

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

Elsewhere in North Dakota

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.