Bad Air Days in Lyon County, Minnesota: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 375 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (90% particle days).

Which months to watch

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

What actually helps here

Bad air days are rare here. A standard furnace filter is enough; no purifier needed for outdoor air.
On the odd bad day, check AirNow and keep windows shut.

The worst days on file

In 2000 to 2009 this county averaged 2 bad days a year; in 2016 to 2025, 3. Not much has changed. The worst recent year was 2023, with 13 bad days on 361 monitored days.

Date	AQI	Main pollutant
2021-07-30	187	PM2.5
2021-07-29	182	PM2.5
2023-05-18	173	PM2.5
2022-11-01	172	PM2.5
2022-02-22	167	PM2.5

Most days, not the worst ones

Across 3,610 monitored days from 2016 to 2025, the air in Lyon County rated Good on 80% of them, more often than the 72% typical of monitored counties, and Moderate on 19%. The median day sat at AQI 37; one day in ten went above 59.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)55%1,974 days
ozone44%1,579 days
coarse dust (PM10)2%57 days

Lyon County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	281	77	7	2	37	161
2024	366	276	88	2	0	40	142
2023	361	206	142	13	3	46	173
2022	356	303	51	2	2	38	172
2021	359	263	91	5	2	39	187
2020	360	309	51	0	0	35	80
2019	362	306	56	0	0	34	87
2018	365	308	57	0	0	36	86
2017	360	307	53	0	0	35	96
2016	356	327	28	1	0	32	110
2015	365	310	54	1	0	33	119
2014	364	290	73	1	0	37	109
2013	365	263	100	2	0	41	101
2012	364	245	117	2	0	43	101
2011	356	267	88	1	0	41	101
2010	355	155	197	3	0	52	109

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

Minnesota compared

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.