Bad Air Days in Vilas County, Wisconsin: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 523 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (56% particle days).

The bad-air season here

Most bad days here fall in June and May and July and August. 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 4 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 12 bad days on 340 monitored days.

Date	AQI	Main pollutant
2023-06-26	168	PM2.5
2023-06-28	163	PM2.5
2021-08-03	148	PM2.5
2021-07-31	120	PM2.5
2023-05-30	119	Ozone

The air on a normal day

Across 3,081 monitored days from 2016 to 2025, the air in Vilas County rated Good on 87% of them, more often than the 72% typical of monitored counties, and Moderate on 12%. The median day sat at AQI 35; one day in ten went above 54.

The pollutant setting the AQI on an ordinary day here:

ozone57%1,755 days
fine particles (PM2.5)43%1,326 days

Vilas County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	199	183	15	1	0	36	105
2024	204	197	7	0	0	37	93
2023	340	247	81	12	2	39	168
2022	363	329	34	0	0	33	68
2021	363	297	63	3	0	34	148
2020	366	327	39	0	0	33	84
2019	362	320	42	0	0	31	91
2018	360	298	62	0	0	39	100
2017	319	294	25	0	0	34	80
2016	205	189	16	0	0	32	77
2015	204	186	18	0	0	34	84
2014	208	186	21	1	0	35	112
2013	222	203	19	0	0	37	80
2012	222	194	27	1	0	36	108
2011	223	199	24	0	0	36	97
2010	230	205	25	0	0	37	97

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

Wisconsin 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, and on why a purifier does not touch ozone in smoke vs ozone.