Charleston, SC Air Quality in December
Across 2019–2025, Charleston's December air quality had a median AQI of 44 (Good) over 217 monitored days in the Charleston-North Charleston, SC area. 0.0% of December days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 80.6% of days. The cleanest December on record here was 2019 (median AQI 33, 0 days above 100) and the worst was 2021 (median 53, 0 days above 100, peak AQI 80).
- Good: 64.1%
- Moderate: 35.9%
- Unhealthy for Sensitive Groups: 0.0%
- 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.
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How is the air in Charleston in December?
Good on a typical day: median AQI 44 across 2019–2025, with 0.0% of December days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓64.1% of December days were Good (AQI 0–50), 35.9% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the December peak was 89.
- ✓Best December: 2019; worst December: 2021.
Frequently asked questions
What is the air quality like in Charleston in December?▾
Across 2019–2025, the median daily AQI in Charleston in December was 44 (Good). 64.1% of days were Good, 35.9% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Charleston?▾
A typical December day in Charleston sits in the Good range (median AQI 44), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
Which pollutant causes Charleston's December air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 80.6% of December days in Charleston. The highest December AQI recorded in 2019–2025 was 89 (Moderate), in 2021.
Charleston December air quality, year by year
Charleston December air quality by year (Charleston-North Charleston, SC, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 31 | 33 | 0 | 55 | PM2.5 |
| 2020 | 31 | 51 | 0 | 82 | PM2.5 |
| 2021worst | 31 | 53 | 0 | 80 | PM2.5 |
| 2022 | 31 | 44 | 0 | 71 | PM2.5 |
| 2023 | 31 | 39 | 0 | 55 | PM2.5 |
| 2024 | 31 | 39 | 0 | 63 | PM2.5 |
| 2025 | 31 | 52 | 0 | 89 | PM2.5 |
What December air means in Charleston
A typical December day in Charleston sits in the Good range (median AQI 44), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of December days reached AQI 101+ in 2019–2025.
December's median AQI of 44 is in line with Charleston's whole-year median of 47, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Charleston runs above the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Charleston's winter season (December, January, February); the winter page pools all three months.
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 month 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.