Bad Air Days in Boone County, Indiana: 3 a Year

3 bad air days a year

About the middle of monitored US counties. Ranked 403 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (0% particle days).

The bad-air season here

Most bad days here fall in June and May and September. 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 record for Boone

In 2000 to 2009 this county averaged 36 bad days a year; in 2016 to 2025, 3. The air has improved. The worst recent year was 2023, with 9 bad days on 362 monitored days.

Date	AQI	Main pollutant
2023-06-28	185	Ozone
2023-07-25	129	Ozone
2016-06-13	126	Ozone
2023-06-02	126	Ozone
2023-05-24	119	Ozone

An ordinary day in Boone

Across 3,292 monitored days from 2016 to 2025, the air in Boone County rated Good on 89% of them, more often than the 72% typical of monitored counties, and Moderate on 10%. The median day sat at AQI 35; one day in ten went above 53.

The pollutant setting the AQI on an ordinary day here:

ozone100%3,292 days

Boone County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	350	314	33	3	0	35	112
2024	359	313	46	0	0	36	93
2023	362	307	46	9	1	37	185
2022	362	331	30	1	0	36	115
2021	365	337	27	1	0	33	101
2020	352	330	20	2	0	32	101
2019	351	320	31	0	0	35	90
2018	365	324	36	5	0	34	112
2017	245	219	25	1	0	39	101
2016	181	143	35	3	0	40	126
2015	176	144	32	0	0	42	97
2014	183	143	38	2	0	42	108
2013	183	143	38	2	0	43	112
2012	171	99	56	16	1	49	164
2011	204	149	51	4	1	43	159
2010	183	125	51	7	0	45	122

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

Elsewhere in Indiana

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.