Philadelphia Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Philadelphia (Philadelphia-Camden-Wilmington, PA-NJ-DE-MD area) was June 7, 2023, when the daily AQI reached 331 (Hazardous), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 10 of the 10 worst days were Unhealthy (AQI 151+) or worse; 8 of the 10 were driven by fine particulate matter (PM2.5) and 2 by ground-level ozone, and 6 of them fell in 2023. The cleanest day was October 13, 2020 at AQI 21 (Good); the 10 best days span 7 different years.
Reduce Indoor Ozone in Philadelphia
Today's main pollutant in Philadelphia is ground-level ozone (AQI 44). 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 Philadelphia's worst and best air quality days?
Worst: June 7, 2023, AQI 331 (Hazardous, PM2.5). Best: October 13, 2020, AQI 21 (Good). Based on 2,557 EPA-monitored days in the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD area, 2019–2025.
- ✓10 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 151 (Unhealthy).
- ✓Fine particulate matter (PM2.5) drove 8 of the 10 worst days.
- ✓2023 accounts for 6 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Philadelphia?▾
June 7, 2023: the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD area's daily AQI hit 331 (Hazardous), driven by fine particulate matter (PM2.5), in wildfire smoke season. That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Philadelphia?▾
October 13, 2020, with a daily AQI of 21 (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 Philadelphia's worst air quality day in 2025?▾
February 21, 2025, AQI 168 (Unhealthy), set by fine particulate matter (PM2.5).
Which pollutant causes Philadelphia's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 8 of the 10 worst days; ground-level ozone on 2. The tables above list the defining pollutant for every day.
Philadelphia's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD 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) | 331 | Hazardous | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 246 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 200 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
| 4 | (2023 page) | 176 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2025 page) | 168 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2023 page) | 165 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2025 page) | 161 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 8 | (2023 page) | 158 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 9 | (2021 page) | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2021 page) | 151 | Unhealthy | O3 — ground-level ozone, in peak ozone season |
Worst day of each year in Philadelphia
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 | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2020 | 143 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2021 | 153 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2022 | 126 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2023 | 331 | Hazardous | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 150 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 168 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
Philadelphia's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2020 page) | 21 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2023 page) | 22 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2024 page) | 24 | Good | O3 — ground-level ozone |
| 4 | (2025 page) | 25 | Good | O3 — ground-level ozone |
| 5 | (2019 page) | 25 | Good | NO2 — nitrogen dioxide |
| 6 | (2024 page) | 26 | Good | O3 — ground-level ozone |
| 7 | (2022 page) | 26 | Good | O3 — ground-level ozone |
| 8 | (2021 page) | 26 | Good | O3 — ground-level ozone |
| 9 | (2022 page) | 27 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2020 page) | 27 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Philadelphia
The latest EPA AirNow observation puts Philadelphia's AQI at 44 (O3). The days above are historical records, not today's reading.
View current Philadelphia air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Philadelphia-Camden-Wilmington, PA-NJ-DE-MD), 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.