Harrisburg Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Harrisburg (Harrisburg-Carlisle, PA area) was June 8, 2023, when the daily AQI reached 255 (Very Unhealthy), set by fine particulate matter (PM2.5), in wildfire smoke season. Across 2,557 monitored days in 2019–2025, 6 of the 10 worst days were Unhealthy (AQI 151+) or worse; 10 of the 10 were driven by fine particulate matter (PM2.5), and 6 of them fell in 2023. The cleanest day was October 3, 2019 at AQI 11 (Good); the 10 best days span 7 different years.
Reduce Indoor Ozone in Harrisburg
Today's main pollutant in Harrisburg is ground-level ozone (AQI 48). 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 Harrisburg's worst and best air quality days?
Worst: June 8, 2023, AQI 255 (Very Unhealthy, PM2.5). Best: October 3, 2019, AQI 11 (Good). Based on 2,557 EPA-monitored days in the Harrisburg-Carlisle, PA area, 2019–2025.
- ✓6 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 137 (Unhealthy for Sensitive Groups).
- ✓Fine particulate matter (PM2.5) drove 10 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 Harrisburg?▾
June 8, 2023: the Harrisburg-Carlisle, PA area's daily AQI hit 255 (Very Unhealthy), 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 Harrisburg?▾
October 3, 2019, with a daily AQI of 11 (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 Harrisburg's worst air quality day in 2025?▾
August 5, 2025, AQI 101 (Unhealthy for Sensitive Groups), set by ground-level ozone, in peak ozone season.
Which pollutant causes Harrisburg's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 10 of the 10 worst days. The tables above list the defining pollutant for every day.
Harrisburg's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Harrisburg-Carlisle, PA 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) | 255 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 2 | (2023 page) | 232 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 3 | (2023 page) | 180 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 4 | (2023 page) | 164 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 5 | (2019 page) | 161 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2023 page) | 152 | Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 7 | (2019 page) | 150 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2019 page) | 149 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2023 page) | 144 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season |
| 10 | (2020 page) | 137 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
Worst day of each year in Harrisburg
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 | 161 | Unhealthy | PM2.5 — fine particulate matter (PM2.5) | |
| 2020 | 137 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) | |
| 2021 | 127 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2022 | 127 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) | |
| 2023 | 255 | Very Unhealthy | PM2.5 — fine particulate matter (PM2.5), in wildfire smoke season | |
| 2024 | 105 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season | |
| 2025 | 101 | Unhealthy for Sensitive Groups | O3 — ground-level ozone, in peak ozone season |
Harrisburg's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Harrisburg-Carlisle, PA area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2019 page) | 11 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2021 page) | 14 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2025 page) | 16 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2020 page) | 17 | Good | O3 — ground-level ozone |
| 5 | (2023 page) | 18 | Good | O3 — ground-level ozone |
| 6 | (2022 page) | 18 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2025 page) | 20 | Good | O3 — ground-level ozone |
| 8 | (2024 page) | 20 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2022 page) | 20 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2021 page) | 20 | Good | PM2.5 — fine particulate matter (PM2.5) |
Right now in Harrisburg
The latest EPA AirNow observation puts Harrisburg's AQI at 48 (O3). The days above are historical records, not today's reading.
View current Harrisburg air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Harrisburg-Carlisle, PA), 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.