Median AQI
41
Good
South Carolina · County air quality · 2025
Horry County, South Carolina
Median AQI 41 (Good). 79.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 41
- Median AQI
- 79.8%
- Good-air days
- 2
- Unhealthy days
- 52%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Horry County's air is good on balance, cleaner than the median US county, a median AQI of 41 with 79.8% of 273 monitored days in the Good band, driven mainly by Ozone.
- 41
- median AQI · Good
- 79.8%
- days rated Good
- Ozone
- main pollutant
- 52%
- cleaner than US counties
2 days reached Unhealthy or worse; the worst single reading hit AQI 170.
Data updated July 2026
- Good · 218 d · 79.9%
- Moderate · 52 d · 19.0%
- USG · 1 d · 0.4%
- Unhealthy · 2 d · 0.7%
How did Horry County's air break down in 2025?
Across 273 monitored days, 218 fell in the Good band (AQI 0–50) and 2 reached Unhealthy or worse. The worst single day peaked at AQI 170 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 41 (Good).
Insights: Horry County, South Carolina. EPA monitors recorded a median Air Quality Index of 41 across 273 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 218 (80%) fell in the Good band (AQI 0–50), 52 (19%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 57, while the worst single-day peak hit 170 (Unhealthy). Residents averaged about 24.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (140 days), PM2.5 (133 days). Across the 2020–2025 trend window, good days shifted by +4 and the median AQI moved +9 points, placing the multi-year trajectory at worsening. Residents and visitors experienced 2 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Aiken (89.1% good, AQI 39); Anderson (90.0% good, AQI 41); Berkeley (92.2% good, AQI 36); Charleston (59.0% good, AQI 47); Chesterfield (61.2% good, AQI 46); Darlington (87.3% good, AQI 42).
Air Quality Summary
Good Days
79.8%
218 of 273 monitored days
4.8pp vs 75% target
Max AQI Recorded
170
Unhealthy
Health Grade
Good
90th-pct AQI 57
Horry County, Good days share 79.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Horry County, Unhealthy-or-worse share 0.7%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
218
80%
Moderate
52
19%
USG
1
0%
Unhealthy
2
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Horry County.
- Ozone · 140 days · 51.3%
- PM2.5 · 133 days · 48.7%
Health Impact Assessment
Good
Horry County's air quality is rated Good based on 79.8% good air days. There were 2 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 1 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 170. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 140 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Horry County. Best year: 2024 (287 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 214 | 0 | 0 | 0 | 32 | 50 |
| 2021 | 238 | 26 | 0 | 0 | 38 | 90 |
| 2022 | 247 | 16 | 0 | 0 | 38 | 93 |
| 2023 | 238 | 94 | 0 | 0 | 43 | 100 |
| 2024 | 287 | 77 | 0 | 0 | 40 | 87 |
| 2025 | 218 | 52 | 1 | 2 | 41 | 170 |
How does Horry County compare?
How Horry County compares
Good-day share better than US avg
Horry County 79.8%
Aiken County, South Carolina 89.1%
US average 76.5%
Median AQI worse than US avg
Horry County 41
Aiken County, South Carolina 39
US average 38
Unhealthy days / yr worse than US avg
Horry County 2
Aiken County, South Carolina 0
US average 0
Other Counties in South Carolina
Air quality comparison for nearby counties in South Carolina.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Horry County.
Albemarle County, Virginia
AQI 41 · 77.9% good
Anderson County, South Carolina
AQI 41 · 90.0% good
Berkshire County, Massachusetts
AQI 41 · 71.6% good
Berrien County, Michigan
AQI 41 · 80.9% good
Blair County, Pennsylvania
AQI 41 · 71.9% good
Bonner County, Idaho
AQI 41 · 71.3% good
What Horry County's air means for you
On most days the air here is fine, but Ozone drives 2 unhealthy-or-worse days a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 41 means for exposure. Health guidance
- See how Horry County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Horry County with its South Carolina neighbours before drawing a conclusion about the region. All of South Carolina
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Horry County, South Carolina? ▼
Horry County has a median Air Quality Index (AQI) of 41, rated "Good." 79.8% of monitored days (218 out of 273) had good air quality in 2025.
What is the main pollutant in Horry County? ▼
The primary pollutant in Horry County is Ozone (O3), which was the main AQI driver on 140 days (51% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Horry County have? ▼
In 2025, Horry County recorded 2 unhealthy air days (2 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 170.
Is the air quality in Horry County getting better or worse? ▼
Air quality in Horry County is worsening based on 5-year trends (2020-2025). Best year: 2024 with 287 good days. Worst year: 2020 with 214 good days.
What does AQI 41 mean for health? ▼
Horry County's median AQI of 41 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Horry County compare to other counties in South Carolina? ▼
Horry County has 79.8% good air days. Nearby counties in South Carolina: Aiken (89.1% good), Anderson (90.0% good), Berkeley (92.2% good), Charleston (59.0% good), Chesterfield (61.2% good), Darlington (87.3% good).
What is the 90th percentile AQI in Horry County? ▼
The 90th percentile AQI for Horry County is 57, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 170 (Unhealthy).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.