Horry County, South Carolina air quality history

Daily Air Quality Index summaries from EPA monitors in Horry, South Carolina, 1980–2025.

82%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

325

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Horry, South Carolina on 325 days. 268 of those days (82%) were in the Good range, and the median daily AQI was 39. That median is lower than the typical monitored county in South Carolina (median 43 across 13 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 173 days. Across the years with fuller monitoring, the share of Good days rose: an average of 62% in 1980–1982 versus 78% in 2023–2025.

Years with fewer than 120 monitored days (2003, 2004, 2005, 2006, 2007, 2019…) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median daily AQI
90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

Pollutant	Days as main pollutant	Share of monitored days
Ozone	173	53%
Fine particles (PM2.5)	152	47%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	325	268	54	1	2	39	55	170	Ozone
2024	364	287	77	0	0	40	55	87	PM2.5
2023	332	238	94	0	0	43	62	100	PM2.5
2022	263	247	16	0	0	38	49	93	Ozone
2021	264	238	26	0	0	38	50	90	Ozone
2020	214	214	0	0	0	32	44	50	Ozone
2019	101	99	2	0	0	35	44	77	Ozone
2018	180	164	16	0	0	37	50	87	Ozone
2017	354	350	4	0	0	32	44	64	Ozone
2016	136	136	0	0	0	26	33	39	Ozone
2011	259	225	34	0	0	41	58	90	Ozone
2010	239	204	34	1	0	41	58	101	Ozone
2009	147	143	4	0	0	22	37	55	PM10
2007	96	41	53	2	0	52	72	129	PM2.5
2006	111	44	67	0	0	53	72	93	PM2.5
2005	119	38	80	1	0	56	75	121	PM2.5
2004	118	41	77	0	0	55	70	92	PM2.5
2003	119	42	77	0	0	54	65	87	PM2.5
2002	115	46	68	0	1	54	69	166	PM2.5
2001	114	41	73	0	0	55	69	90	PM2.5
2000	5	2	3	0	0	52	57	57	PM2.5
1983	210	128	57	20	5	46	112	200	Ozone
1982	168	117	39	10	2	43	90	164	Ozone
1981	184	114	52	15	3	46	100	172	Ozone
1980	163	90	57	15	1	47	100	159	Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in South Carolina with a similar median AQI in 2025

All monitored counties in South Carolina

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem