Philadelphia Air Quality in January
Across 2019–2025, Philadelphia's January air quality had a median AQI of 57 (Moderate) over 217 monitored days in the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD area. 1.4% of January days (3 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 90.8% of days. The cleanest January on record here was 2024 (median AQI 55, 0 days above 100) and the worst was 2019 (median 64, 2 days above 100, peak AQI 131).
- Good: 26.3%
- Moderate: 72.4%
- Unhealthy for Sensitive Groups: 1.4%
- Unhealthy or worse: 0.0%
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.
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How is the air in Philadelphia in January?
Moderate on a typical day: median AQI 57 across 2019–2025, with 1.4% of January days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓26.3% of January days were Good (AQI 0–50), 72.4% Moderate (51–100).
- ✓3 days of 217 reached AQI 101+; the January peak was 131.
- ✓Best January: 2024; worst January: 2019.
Frequently asked questions
What is the air quality like in Philadelphia in January?▾
Across 2019–2025, the median daily AQI in Philadelphia in January was 57 (Moderate). 26.3% of days were Good, 72.4% Moderate, and 1.4% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is January a good time for outdoor exercise in Philadelphia?▾
A typical January day in Philadelphia is Moderate (median AQI 57): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 71 of January 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 Philadelphia's January air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 90.8% of January days in Philadelphia. The highest January AQI recorded in 2019–2025 was 131 (Unhealthy for Sensitive Groups), in 2019.
Philadelphia January air quality, year by year
Philadelphia January air quality by year (Philadelphia-Camden-Wilmington, PA-NJ-DE-MD, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019worst | 31 | 64 | 2 | 131 | PM2.5 |
| 2020 | 31 | 56 | 1 | 103 | PM2.5 |
| 2021 | 31 | 56 | 0 | 99 | PM2.5 |
| 2022 | 31 | 57 | 0 | 95 | PM2.5 |
| 2023 | 31 | 58 | 0 | 85 | PM2.5 |
| 2024cleanest | 31 | 55 | 0 | 91 | PM2.5 |
| 2025 | 31 | 56 | 0 | 82 | PM2.5 |
What January air means in Philadelphia
A typical January day in Philadelphia is Moderate (median AQI 57): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 71 of January days (1.4%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
January's median AQI of 57 is in line with Philadelphia's whole-year median of 56, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median January AQI across every EPA metro area (95,602 metro-days, 2019–2025) is 39, so Philadelphia runs above the national January norm; 1.4% of its January days topped AQI 100 versus 0.7% nationally (about the same).
January is part of Philadelphia's winter season (December, January, February); the winter page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Philadelphia
The latest EPA AirNow observation puts Philadelphia's AQI at 44 (O3). The figures above are multi-year month statistics, 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.