The Washington year in pollen
Pollen seasons in Washington: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around November 18.
Tree pollen
Grass
Ragweed
When does ragweed season end in Washington?
Ragweed season in Washington typically ends with the first frost, around November 18. Some years it comes as early as November 12, some as late as November 25.
A light frost around November 18 knocks the season down; the hard freeze that finishes it usually follows by December 3. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Washington 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 District of Columbia page.
Frost dates for Washington come from the Washington Reagan Airport weather station's 30-year records. Season windows reviewed August 2026.