Bad Air Days in Vigo County, Indiana: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 504 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly ozone: summer smog (40% particle days).

When the bad days come in Vigo

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.

The worst days on file

In 2000 to 2009 this county averaged 17 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 8 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-28	232	PM2.5
2023-06-27	164	PM2.5
2023-06-02	126	Ozone
2023-05-24	122	Ozone
2023-06-24	119	Ozone

The air on a normal day

Across 3,650 monitored days from 2016 to 2025, the air in Vigo County rated Good on 52% of them, less often than the 72% typical of monitored counties, and Moderate on 48%. The median day sat at AQI 49; one day in ten went above 66.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)68%2,465 days
ozone32%1,185 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	218	146	1	0	45	108
2024	366	204	161	1	0	47	112
2023	365	182	175	8	2	51	232
2022	365	203	160	2	0	47	115
2021	365	172	193	0	0	51	99
2020	366	223	142	1	0	46	112
2019	365	161	203	1	0	52	102
2018	365	188	174	3	0	50	115
2017	365	153	210	2	0	52	105
2016	363	180	182	1	0	51	108
2015	362	165	196	1	1	52	151
2014	354	136	216	2	0	54	134
2013	362	149	213	0	0	53	97
2012	355	125	219	11	0	55	136
2011	360	114	239	7	0	58	127
2010	362	108	252	2	0	57	115

*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.