Bad Air Days in Charleston County, South Carolina: under 1 a Year

under 1 bad air day a year

Fewer bad air days than most monitored US counties. Ranked 725 of 996 monitored counties, where 1 is worst.

What makes them bad: mostly particles: smoke and dust (88% particle days).

Which months to watch

Most bad days here fall in November and February and May and June. 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 Charleston

In 2000 to 2009 this county averaged 8 bad days a year; in 2016 to 2025, under 1. The air has improved. The worst recent year was 2016, with 5 bad days on 360 monitored days.

Date	AQI	Main pollutant
2016-11-16	160	PM2.5
2016-11-15	156	PM2.5
2016-02-11	119	PM2.5
2016-11-17	117	PM2.5
2020-06-27	117	PM2.5

Most days, not the worst ones

Across 3,629 monitored days from 2016 to 2025, the air in Charleston County rated Good on 65% of them, less often than the 72% typical of monitored counties, and Moderate on 34%. The median day sat at AQI 45; one day in ten went above 59.

The pollutant setting the AQI on an ordinary day here:

fine particles (PM2.5)77%2,810 days
ozone22%804 days

Year by year

Year	Days monitored	Good	Moderate	Over 100	Over 150	Median AQI	Highest AQI
2025*	365	222	142	1	0	47	105
2024	366	269	97	0	0	43	77
2023	365	212	153	0	0	47	93
2022	365	209	156	0	0	47	84
2021	365	197	168	0	0	48	93
2020	366	264	101	1	0	43	117
2019	357	262	95	0	0	42	76
2018	359	269	90	0	0	41	79
2017	361	231	129	1	0	44	101
2016	360	239	116	5	2	44	160
2015	365	256	108	1	0	43	114
2014	365	193	172	0	0	48	80
2013	365	228	137	0	0	44	84
2012	366	148	217	1	0	52	134
2011	365	146	215	4	1	53	153
2010	365	157	206	2	0	52	112

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

Elsewhere in South Carolina

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.