Charleston Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Charleston (Charleston-North Charleston, SC area) was June 27, 2020, when the daily AQI reached 117 (Unhealthy for Sensitive Groups), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,549 monitored days in 2019–2025, 0 of the 10 worst days were Unhealthy (AQI 151+) or worse; 5 of the 10 were driven by ground-level ozone and 4 by fine particulate matter (PM2.5), and 5 of them fell in 2023. The cleanest day was November 21, 2024 at AQI 18 (Good); the 10 best days span 4 different years.
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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When were Charleston's worst and best air quality days?
Worst: June 27, 2020, AQI 117 (Unhealthy for Sensitive Groups, PM2.5). Best: November 21, 2024, AQI 18 (Good). Based on 2,549 EPA-monitored days in the Charleston-North Charleston, SC area, 2019–2025.
- ✓0 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 85 (Moderate).
- ✓Ground-level ozone drove 5 of the 10 worst days.
- ✓2023 accounts for 5 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Charleston?▾
June 27, 2020: the Charleston-North Charleston, SC area's daily AQI hit 117 (Unhealthy for Sensitive Groups), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,549 monitored days in 2019–2025.
What was the best air quality day in Charleston?▾
November 21, 2024, with a daily AQI of 18 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Charleston's worst air quality day in 2025?▾
February 26, 2025, AQI 105 (Unhealthy for Sensitive Groups), set by fine particulate matter (PM2.5).
Which pollutant causes Charleston's worst air days?▾
Ground-level ozone set the AQI on 5 of the 10 worst days; fine particulate matter (PM2.5) on 4. The tables above list the defining pollutant for every day.
Charleston's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Charleston-North Charleston, SC area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 117 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2025 page) | 105 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2023 page) | 105 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
| 4 | (2023 page) | 101 | Unhealthy for Sensitive Groups | O3 — ground-level ozone |
| 5 | (2023 page) | 97 | Moderate | O3 — ground-level ozone |
| 6 | (2023 page) | 93 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2021 page) | 93 | Moderate | O3 — ground-level ozone |
| 8 | (2024 page) | 90 | Moderate | O3 — ground-level ozone |
| 9 | (2025 page) | 89 | Moderate | PM10 — coarse dust (PM10) |
| 10 | (2023 page) | 85 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
Worst day of each year in Charleston
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 76 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2020 | 117 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 93 | Moderate | O3 — ground-level ozone | |
| 2022 | 84 | Moderate | O3 — ground-level ozone | |
| 2023 | 105 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2024 | 90 | Moderate | O3 — ground-level ozone | |
| 2025 | 105 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
Charleston's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Charleston-North Charleston, SC area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2024 page) | 18 | Good | NO2 — nitrogen dioxide |
| 2 | (2021 page) | 19 | Good | O3 — ground-level ozone |
| 3 | (2019 page) | 19 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2019 page) | 19 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2024 page) | 21 | Good | O3 — ground-level ozone |
| 6 | (2024 page) | 21 | Good | O3 — ground-level ozone |
| 7 | (2021 page) | 21 | Good | O3 — ground-level ozone |
| 8 | (2019 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2019 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2020 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Charleston
The latest EPA AirNow observation puts Charleston's AQI at 31 (O3). The days above are historical records, 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.