Bad Air Days in Johnson County, Texas: 7 a Year

7 bad air days a year

More bad air days than three quarters of monitored counties. Ranked 144 of 996 monitored counties, where 1 is worst.

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

When the bad days come in Johnson

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

Is a purifier worth it here?

Ozone drives many bad days here. Purifiers and filters do not remove ozone, so do not buy one for that. Ozone peaks on hot afternoons: exercise outside in the morning.

Better or worse than it was

In 2000 to 2009 this county averaged 25 bad days a year; in 2016 to 2025, 7. The air has improved. The worst recent year was 2022, with 14 bad days on 362 monitored days.

Date	AQI	Main pollutant
2018-08-21	156	Ozone
2022-08-11	156	Ozone
2016-06-07	150	Ozone
2017-06-07	147	Ozone
2018-07-23	143	Ozone

The air on a normal day

Across 3,562 monitored days from 2016 to 2025, the air in Johnson County rated Good on 83% of them, more often than the 72% typical of monitored counties, and Moderate on 15%. The median day sat at AQI 38; one day in ten went above 64.

The pollutant setting the AQI on an ordinary day here:

ozone100%3,562 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	351	300	50	1	0	37	101
2024	350	286	54	10	0	39	129
2023	362	283	71	8	0	38	126
2022	362	281	67	14	1	41	156
2021	363	311	46	6	0	37	136
2020	349	320	27	2	0	34	105
2019	352	298	47	7	0	38	143
2018	354	302	44	8	1	35	156
2017	362	293	61	8	0	41	147
2016	357	300	53	4	0	40	150
2015	361	300	55	6	1	35	156
2014	361	307	50	4	0	36	129
2013	352	289	52	11	0	37	143
2012	353	283	55	15	1	38	203
2011	359	284	58	17	1	38	161
2010	355	310	38	7	0	36	140

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

Texas 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, and on why a purifier does not touch ozone in smoke vs ozone.