Bad Air Days in Johnson County, Kansas: 2 a Year

2 bad air days a year

Fewer bad air days than most monitored US counties. Ranked 518 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (63% particle days).

Which months to watch

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

What to buy, and what not to

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 8 bad days a year; in 2016 to 2025, 2. The air has improved. The worst recent year was 2023, with 10 bad days on 365 monitored days.

Date	AQI	Main pollutant
2025-03-14	188	PM10
2023-09-15	165	PM10
2023-06-06	164	Ozone
2025-08-01	157	PM2.5
2023-07-12	151	PM10

An ordinary day in Johnson

Across 3,645 monitored days from 2016 to 2025, the air in Johnson County rated Good on 70% of them, close to the 72% typical of monitored counties, and Moderate on 29%. The median day sat at AQI 42; one day in ten went above 60.

The pollutant setting the AQI on an ordinary day here:

ozone51%1,848 days
fine particles (PM2.5)49%1,779 days

Johnson County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	250	112	3	2	44	188
2024	366	257	109	0	0	44	80
2023	365	189	166	10	3	49	165
2022	365	227	137	1	0	44	115
2021	364	207	153	4	0	46	138
2020	365	250	114	1	0	41	117
2019	362	308	54	0	0	38	77
2018	363	277	86	0	0	40	92
2017	364	281	83	0	0	40	100
2016	366	315	51	0	0	37	87
2015	365	309	56	0	0	35	100
2014	365	311	54	0	0	37	84
2013	364	286	78	0	0	40	87
2012	364	243	100	21	3	41	161
2011	364	249	105	10	1	42	161
2010	359	266	89	4	0	41	112

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

Nearby counties on file

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.