Bad Air Days in Perry County, Missouri: 2 a Year

2 bad air days a year

About the middle of monitored US counties. Ranked 448 of 996 monitored counties, where 1 is worst.

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

Which months to watch

Most bad days here fall in June and May. 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 19 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 11 bad days on 245 monitored days.

Date	AQI	Main pollutant
2023-06-10	150	Ozone
2023-06-03	147	Ozone
2023-06-23	143	Ozone
2023-06-06	133	Ozone
2018-06-06	126	Ozone

Most days, not the worst ones

Across 2,434 monitored days from 2016 to 2025, the air in Perry County rated Good on 85% of them, more often than the 72% typical of monitored counties, and Moderate on 14%. The median day sat at AQI 41; one day in ten went above 57.

The pollutant setting the AQI on an ordinary day here:

ozone100%2,434 days

Perry County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	255	216	38	1	0	41	105
2024	251	218	33	0	0	42	93
2023	245	179	55	11	0	44	150
2022	245	211	34	0	0	42	97
2021	244	213	29	2	0	39	122
2020	245	231	14	0	0	36	97
2019	245	224	21	0	0	40	87
2018	245	208	36	1	0	39	126
2017	245	202	43	0	0	44	100
2016	214	173	40	1	0	42	119
2015	214	178	35	1	0	41	129
2014	214	176	38	0	0	40	97
2013	214	178	36	0	0	42	100
2012	214	124	65	25	1	48	159
2011	243	166	70	7	0	46	129
2010	214	131	76	7	0	47	133

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

Elsewhere in Missouri

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.