Harrisburg Air Quality in Winter
Across 2019–2025, Harrisburg's winter (December–February) air quality had a median AQI of 52 (Moderate) over 632 monitored days in the Harrisburg-Carlisle, PA area. 1.4% of winter days (9 of 632) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 88.1% of days. The cleanest winter on record here was 2024 (median AQI 49, 0 days above 100) and the worst was 2019 (median 55, 4 days above 100, peak AQI 150).
- Good: 44.9%
- Moderate: 53.6%
- Unhealthy for Sensitive Groups: 1.4%
- Unhealthy or worse: 0.0%
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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How is the air in Harrisburg in winter?
Moderate on a typical day: median AQI 52 across 2019–2025, with 1.4% of winter days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓44.9% of winter days were Good (AQI 0–50), 53.6% Moderate (51–100).
- ✓9 days of 632 reached AQI 101+; the winter peak was 150.
- ✓Cleanest month: January; worst month: December.
Frequently asked questions
What is the air quality like in Harrisburg in winter?▾
Across 2019–2025, the median daily AQI in Harrisburg in winter was 52 (Moderate). 44.9% of days were Good, 53.6% Moderate, and 1.4% reached Unhealthy for Sensitive Groups or worse, based on 632 monitored days in EPA's Air Quality System.
Is winter a good time for outdoor exercise in Harrisburg?▾
A typical winter day in Harrisburg is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 71 of winter days (1.4%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Which pollutant causes Harrisburg's winter air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 88.1% of winter days in Harrisburg. The highest winter AQI recorded in 2019–2025 was 150 (Unhealthy for Sensitive Groups), in 2019.
Harrisburg winter air quality, year by year
Harrisburg winter air quality by year (Harrisburg-Carlisle, PA, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 90 | 55 | 4 | 150 | PM2.5 |
| 2020 | 91 | 49 | 3 | 137 | PM2.5 |
| 2021 | 90 | 55 | 0 | 94 | PM2.5 |
| 2022 | 90 | 54 | 2 | 127 | PM2.5 |
| 2023 | 90 | 53 | 0 | 94 | PM2.5 |
| 2024cleanest | 91 | 49 | 0 | 95 | PM2.5 |
| 2025 | 90 | 49 | 0 | 89 | PM2.5 |
What winter air means in Harrisburg
A typical winter day in Harrisburg is Moderate (median AQI 52): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 71 of winter days (1.4%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
Winter's median AQI of 52 is in line with Harrisburg's whole-year median of 50, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Winter AQI across every EPA metro area (278,620 metro-days, 2019–2025) is 40, so Harrisburg runs above the national Winter norm; 1.4% of its Winter days topped AQI 100 versus 0.6% nationally (about the same).
Within the season, January is the cleanest month (median AQI 52, 0.5% of days above 100) and December the worst (median 52, 2.3% above 100).
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Harrisburg
The latest EPA AirNow observation puts Harrisburg's AQI at 48 (O3). The figures above are multi-year season statistics, 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.