Bad Air Days in Cobb County, Georgia: 1 a Year

1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 663 of 996 monitored counties, where 1 is worst.

What makes them bad: a mix of particles and ozone (44% particle days).

The bad-air season here

Most bad days here fall in June and July 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 35 bad days a year; in 2016 to 2025, 1. The air has improved. The worst recent year was 2016, with 4 bad days on 351 monitored days.

Date	AQI	Main pollutant
2016-06-10	200	Ozone
2016-11-14	139	PM2.5
2023-06-29	125	PM2.5
2016-07-20	119	Ozone
2019-09-13	119	Ozone

An ordinary day in Cobb

Across 2,990 monitored days from 2016 to 2025, the air in Cobb County rated Good on 71% of them, close to the 72% typical of monitored counties, and Moderate on 28%. The median day sat at AQI 43; one day in ten went above 60.

The pollutant setting the AQI on an ordinary day here:

ozone60%1,784 days
fine particles (PM2.5)40%1,206 days

Every recent year on file

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	245	229	16	0	0	35	74
2024	364	202	162	0	0	48	86
2023	323	215	105	3	0	43	125
2022	285	231	53	1	0	40	105
2021	285	218	67	0	0	41	80
2020	285	243	42	0	0	36	91
2019	282	191	90	1	0	44	119
2018	286	213	73	0	0	41	100
2017	284	211	73	0	0	43	97
2016	351	177	170	4	1	50	200
2015	359	182	176	1	0	50	112
2014	307	136	169	2	0	52	119
2013	355	180	173	2	0	50	108
2012	360	147	204	9	1	53	154
2011	317	105	195	17	0	55	140
2010	347	107	223	17	1	56	156

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

Elsewhere in Georgia

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.