The Baltimore year in pollen
Pollen seasons in Baltimore: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around November 21.
First frost lands around November 21 in Baltimore — about 17 days later than Maryland overall — which shifts when ragweed season ends here.
When does ragweed season end in Baltimore?
Ragweed season in Baltimore typically ends with the first frost, around November 21. Some years it comes as early as November 15, some as late as November 29.
A light frost around November 21 knocks the season down; the hard freeze that finishes it usually follows by December 5. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Baltimore pollen year
| Allergen | Typical season |
|---|---|
| Oak | March to May |
| Maple | March to April |
| Birch | March to May |
| Ash | March to April |
| Pine | April to June |
| Grass | May to July |
Season-by-season detail is on the Maryland page.
Nearby calendars
Frost dates for Baltimore come from the Md Sci Ctr Baltimore weather station's 30-year records. Season windows reviewed August 2026.