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