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

3 bad air days a year

About the middle of monitored US counties. Ranked 350 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (22% particle days).

Which months to watch

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

Is a purifier worth it 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.

Better or worse than it was

In 2000 to 2009 this county averaged 28 bad days a year; in 2016 to 2025, 3. The air has improved. The worst recent year was 2023, with 11 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-28	182	PM2.5
2024-08-26	150	Ozone
2016-06-10	143	Ozone
2025-06-11	133	Ozone
2023-06-15	124	PM2.5

Most days, not the worst ones

Across 3,641 monitored days from 2016 to 2025, the air in Clark County rated Good on 57% of them, less often than the 72% typical of monitored counties, and Moderate on 42%. The median day sat at AQI 47; one day in ten went above 65.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)60%2,200 days
ozone40%1,441 days

Clark County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	212	150	3	0	46	133
2024	366	216	146	4	0	47	150
2023	365	146	208	11	1	52	182
2022	363	170	192	1	0	51	119
2021	365	160	205	0	0	52	96
2020	366	186	180	0	0	50	92
2019	365	225	139	1	0	45	101
2018	357	276	77	4	0	37	122
2017	364	286	77	1	0	40	101
2016	365	195	163	7	0	49	143
2015	364	160	200	4	1	52	164
2014	335	123	210	2	0	54	122
2013	357	130	227	0	0	54	93
2012	356	116	220	20	3	55	164
2011	342	110	212	20	2	56	161
2010	354	73	265	16	0	61	147

*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.