Bad Air Days in Grant County, Wisconsin: 1 a Year

1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 649 of 996 monitored counties, where 1 is worst.

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

The bad-air season here

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

What to buy, and what not to

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

The worst recent year was 2023, with 7 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-28	221	PM2.5
2023-06-29	186	PM2.5
2023-06-27	181	PM2.5
2025-07-31	167	PM2.5
2023-07-16	138	PM2.5

An ordinary day in Grant

Across 3,507 monitored days from 2016 to 2025, the air in Grant County rated Good on 67% of them, less often than the 72% typical of monitored counties, and Moderate on 33%. The median day sat at AQI 40; one day in ten went above 61.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%3,507 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	358	246	109	3	1	37	167
2024	366	263	103	0	0	36	82
2023	365	198	160	7	3	48	221
2022	359	241	118	0	0	39	80
2021	355	200	155	0	0	46	96
2020	361	235	126	0	0	40	84
2019	365	255	109	1	0	39	104
2018	351	233	118	0	0	42	83
2017	346	265	81	0	0	33	88
2016	281	205	76	0	0	38	81
2015	361	253	107	1	0	39	107
2014	361	234	126	1	0	40	109
2013	356	219	137	0	0	42	79
2012	362	219	143	0	0	43	93
2011	149	82	67	0	0	48	86
2010	120	67	52	1	0	49	124

*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.