Bad Air Days in Johnson County, Iowa: 1 a Year

1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 603 of 996 monitored counties, where 1 is worst.

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

Which months to watch

Most bad days here fall in June and July and August. 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.

Better or worse than it was

In 2000 to 2009 this county averaged 4 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2023, with 6 bad days on 365 monitored days.

Date	AQI	Main pollutant
2023-06-28	210	PM2.5
2023-06-27	200	PM2.5
2023-06-29	187	PM2.5
2025-07-31	159	PM2.5
2023-07-16	156	PM2.5

Most days, not the worst ones

Across 3,643 monitored days from 2016 to 2025, the air in Johnson County rated Good on 58% of them, less often than the 72% typical of monitored counties, and Moderate on 42%. The median day sat at AQI 46; one day in ten went above 62.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)100%3,643 days

Johnson County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	256	105	4	1	37	159
2024	366	259	107	0	0	39	83
2023	365	143	216	6	4	53	210
2022	365	223	141	1	0	44	108
2021	364	172	190	2	0	52	121
2020	362	207	154	1	0	47	105
2019	364	210	154	0	0	46	92
2018	362	186	176	0	0	50	93
2017	364	216	148	0	0	44	82
2016	366	236	130	0	0	44	100
2015	365	198	166	1	0	48	139
2014	364	201	162	1	0	47	108
2013	365	160	204	1	0	53	103
2012	366	119	247	0	0	55	91
2011	364	94	270	0	0	56	97
2010	365	84	277	4	0	57	112

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

Iowa 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.