The Philadelphia year in pollen
Pollen seasons in Philadelphia: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around November 10.
First frost lands around November 10 in Philadelphia — about 13 days later than Pennsylvania overall — which shifts when ragweed season ends here.
When does ragweed season end in Philadelphia?
Ragweed season in Philadelphia typically ends with the first frost, around November 10. Some years it comes as early as November 5, some as late as November 16.
A light frost around November 10 knocks the season down; the hard freeze that finishes it usually follows by November 23. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Philadelphia pollen year
| Allergen | Typical season |
|---|---|
| Maple | March to April |
| Birch | April to May |
| Oak | April to June |
| Ash | April to May |
| Pine | May to June |
| Grass | May to July |
Season-by-season detail is on the Pennsylvania page.
Nearby calendars
Frost dates for Philadelphia come from the Philadelphia International Airport weather station's 30-year records. Season windows reviewed August 2026.