Durham Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Durham (Durham-Chapel Hill, NC area) was June 29, 2023, when the daily AQI reached 121 (Unhealthy for Sensitive Groups), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,551 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 5 by fine particulate matter (PM2.5), and 4 of them fell in 2023. The cleanest day was December 10, 2023 at AQI 3 (Good); the 10 best days span 4 different years.
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When were Durham's worst and best air quality days?
Worst: June 29, 2023, AQI 121 (Unhealthy for Sensitive Groups, PM2.5). Best: December 10, 2023, AQI 3 (Good). Based on 2,551 EPA-monitored days in the Durham-Chapel Hill, NC area, 2019–2025.
- ✓0 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 90 (Moderate).
- ✓Ground-level ozone drove 5 of the 10 worst days.
- ✓2023 accounts for 4 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Durham?▾
June 29, 2023: the Durham-Chapel Hill, NC area's daily AQI hit 121 (Unhealthy for Sensitive Groups), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,551 monitored days in 2019–2025.
What was the best air quality day in Durham?▾
December 10, 2023, with a daily AQI of 3 (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 Durham's worst air quality day in 2025?▾
November 21, 2025, AQI 77 (Moderate), set by fine particulate matter (PM2.5).
Which pollutant causes Durham's worst air days?▾
Ground-level ozone set the AQI on 5 of the 10 worst days; fine particulate matter (PM2.5) on 5. The tables above list the defining pollutant for every day.
Durham's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Durham-Chapel Hill, NC area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 121 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 104 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 104 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2023 page) | 101 | Unhealthy for Sensitive Groups | O3 — ground-level ozone |
| 5 | (2024 page) | 97 | Moderate | O3 — ground-level ozone, in peak ozone season |
| 6 | (2020 page) | 97 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2022 page) | 93 | Moderate | O3 — ground-level ozone, in peak ozone season |
| 8 | (2020 page) | 92 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2021 page) | 90 | Moderate | O3 — ground-level ozone |
| 10 | (2021 page) | 90 | Moderate | O3 — ground-level ozone |
Worst day of each year in Durham
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 | 87 | Moderate | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 97 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2021 | 90 | Moderate | O3 — ground-level ozone | |
| 2022 | 93 | Moderate | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 121 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 97 | Moderate | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 77 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
Durham's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Durham-Chapel Hill, NC area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 3 | Good | PM10 — coarse dust (PM10) |
| 2 | (2020 page) | 3 | Good | PM10 — coarse dust (PM10) |
| 3 | (2024 page) | 6 | Good | PM10 — coarse dust (PM10) |
| 4 | (2023 page) | 6 | Good | PM10 — coarse dust (PM10) |
| 5 | (2023 page) | 6 | Good | PM10 — coarse dust (PM10) |
| 6 | (2023 page) | 6 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2022 page) | 6 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2023 page) | 7 | Good | PM10 — coarse dust (PM10) |
| 9 | (2023 page) | 7 | Good | PM10 — coarse dust (PM10) |
| 10 | (2023 page) | 7 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Durham
The latest EPA AirNow observation puts Durham's AQI at 41 (PM2.5). The days above are historical records, not today's reading.
View current Durham air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Durham-Chapel Hill, NC), 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.