Charleston, SC Air Quality in Winter
Across 2019–2025, Charleston's winter (December–February) air quality had a median AQI of 43 (Good) over 632 monitored days in the Charleston-North Charleston, SC area. 0.2% of winter days (1 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 77.5% of days. The cleanest winter on record here was 2024 (median AQI 39, 0 days above 100) and the worst was 2025 (median 48, 1 day above 100, peak AQI 105).
- Good: 65.5%
- Moderate: 34.3%
- Unhealthy for Sensitive Groups: 0.2%
- Unhealthy or worse: 0.0%
Reduce Indoor Ozone in Charleston
Today's main pollutant in Charleston is ground-level ozone (AQI 31). Important: standard HEPA filters do NOT remove ozone — only a purifier with a substantial activated-carbon bed adsorbs it. The biggest wins are cutting indoor sources (gas appliances, certain "ionizer" purifiers) and ventilating when outdoor ozone is low (early morning). A high-carbon unit helps with the gases and VOCs that linger indoors.
Recommended: Levoit Core 300 — True HEPA + activated carbon · CADR ~141 CFM · rooms up to 219 sq ft
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How is the air in Charleston in winter?
Good on a typical day: median AQI 43 across 2019–2025, with 0.2% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓65.5% of winter days were Good (AQI 0–50), 34.3% Moderate (51–100).
- ✓1 day of 632 reached AQI 101+; the winter peak was 105.
- ✓Cleanest month: January; worst month: February.
Frequently asked questions
What is the air quality like in Charleston in winter?▾
Across 2019–2025, the median daily AQI in Charleston in winter was 43 (Good). 65.5% of days were Good, 34.3% Moderate, and 0.2% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Charleston?▾
A typical winter day in Charleston sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Which pollutant causes Charleston's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 77.5% of winter days in Charleston. The highest winter AQI recorded in 2019–2025 was 105 (Unhealthy for Sensitive Groups), in 2025.
Charleston winter air quality, year by year
Charleston winter air quality by year (Charleston-North Charleston, SC, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 90 | 40 | 0 | 66 | PM2.5 |
| 2020 | 91 | 43 | 0 | 82 | PM2.5 |
| 2021 | 90 | 51 | 0 | 80 | PM2.5 |
| 2022 | 90 | 47 | 0 | 77 | PM2.5 |
| 2023 | 90 | 42 | 0 | 73 | PM2.5 |
| 2024cleanest | 91 | 39 | 0 | 76 | PM2.5 |
| 2025worst | 90 | 48 | 1 | 105 | PM2.5 |
What winter air means in Charleston
A typical winter day in Charleston sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of winter days reached AQI 101+ in 2019–2025.
Winter's median AQI of 43 is below Charleston's whole-year median of 47, making it one of the area's cleaner periods. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Charleston runs in line with the national Winter norm; 0.2% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, January is the cleanest month (median AQI 42, 0.0% of days above 100) and February the worst (median 44, 0.5% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Charleston
The latest EPA AirNow observation puts Charleston's AQI at 31 (O3). The figures above are multi-year season statistics, not today's reading.
View current Charleston air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Charleston-North Charleston, SC), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.