Philadelphia Air Quality in May
Across 2019–2025, Philadelphia's May air quality had a median AQI of 54 (Moderate) over 217 monitored days in the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD area. 1.4% of May days (3 of 217) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 60.4% of days. The cleanest May on record here was 2020 (median AQI 48, 0 days above 100) and the worst was 2024 (median 57, 2 days above 100, peak AQI 129).
- Good: 35.5%
- Moderate: 63.1%
- 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.
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 Philadelphia in May?
Moderate on a typical day: median AQI 54 across 2019–2025, with 1.4% of May days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓35.5% of May days were Good (AQI 0–50), 63.1% Moderate (51–100).
- ✓3 days of 217 reached AQI 101+; the May peak was 129.
- ✓Best May: 2020; worst May: 2024.
Frequently asked questions
What is the air quality like in Philadelphia in May?▾
Across 2019–2025, the median daily AQI in Philadelphia in May was 54 (Moderate). 35.5% of days were Good, 63.1% Moderate, and 1.4% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Philadelphia?▾
A typical May day in Philadelphia is Moderate (median AQI 54): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 71 of May 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 May air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 60.4% of May days in Philadelphia. The highest May AQI recorded in 2019–2025 was 129 (Unhealthy for Sensitive Groups), in 2024.
Philadelphia May air quality, year by year
Philadelphia May 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 |
|---|---|---|---|---|---|
| 2019 | 31 | 53 | 0 | 87 | PM2.5 |
| 2020cleanest | 31 | 48 | 0 | 80 | PM2.5 |
| 2021 | 31 | 53 | 1 | 108 | O3 |
| 2022 | 31 | 55 | 0 | 93 | PM2.5 |
| 2023 | 31 | 58 | 0 | 100 | PM2.5 |
| 2024worst | 31 | 57 | 2 | 129 | PM2.5 |
| 2025 | 31 | 53 | 0 | 90 | PM2.5 |
What May air means in Philadelphia
A typical May day in Philadelphia is Moderate (median AQI 54): outdoor exercise is acceptable for most people, but unusually sensitive individuals should watch for symptoms, and about 1 day in 71 of May days (1.4%) reached AQI 101+ — the level at which EPA advises people with asthma, children and older adults to shorten hard outdoor exertion.
May's median AQI of 54 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 May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Philadelphia runs above the national May norm; 1.4% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Philadelphia's spring season (March, April, May); the spring 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.