The Boston year in pollen
Pollen seasons in Boston: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around November 9.
First frost lands around November 9 in Boston — about 19 days later than Massachusetts overall — which shifts when ragweed season ends here.
When does ragweed season end in Boston?
Ragweed season in Boston typically ends with the first frost, around November 9. Some years it comes as early as November 3, some as late as November 14.
A light frost around November 9 knocks the season down; the hard freeze that finishes it usually follows by November 21. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Boston 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 Massachusetts page.
Nearby calendars
Frost dates for Boston come from the Boston Logan International Airport weather station's 30-year records. Season windows reviewed August 2026.