Bad Air Days in Johnston County, North Carolina: under 1 a Year

under 1 bad air days a year

Rare: among the cleanest-air counties EPA monitors. Ranked 889 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (67% particle days).

When the bad days come in Johnston

Most bad days here fall in June and July and November. 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 record for Johnston

In 2000 to 2009 this county averaged 29 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2016, with 1 bad day on 304 monitored days.

Date	AQI	Main pollutant
2022-06-22	140	Ozone
2023-07-18	115	PM2.5
2016-11-18	107	PM2.5
2022-06-21	100	Ozone
2023-06-09	100	PM2.5

The air on a normal day

Across 3,550 monitored days from 2016 to 2025, the air in Johnston County rated Good on 68% of them, less often than the 72% typical of monitored counties, and Moderate on 31%. The median day sat at AQI 43; one day in ten went above 58.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)68%2,400 days
ozone32%1,150 days

Johnston County by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	283	82	0	0	41	84
2024	365	261	104	0	0	43	84
2023	365	240	124	1	0	44	115
2022	365	271	93	1	0	42	140
2021	365	240	125	0	0	44	97
2020	339	266	73	0	0	39	75
2019	363	224	139	0	0	46	87
2018	354	228	126	0	0	44	90
2017	365	216	149	0	0	46	93
2016	304	201	102	1	0	44	107
2015	262	211	51	0	0	41	93
2014	263	212	51	0	0	42	84
2013	261	213	48	0	0	37	97
2012	263	203	54	6	1	42	177
2011	257	153	97	7	0	47	136
2010	266	144	116	6	0	49	119

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

North Carolina 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.