The Spokane year in pollen
Pollen seasons in Spokane: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around October 12.
Spokane's pollen year runs on a different clock than most of Washington — the seasons below follow Spokane's own climate, not the statewide picture.
When does ragweed season end in Spokane?
Ragweed season in Spokane typically ends with the first frost, around October 12. Some years it comes as early as October 6, some as late as October 18.
A light frost around October 12 knocks the season down; the hard freeze that finishes it usually follows by October 23. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Spokane pollen year
| Allergen | Typical season |
|---|---|
| Juniper | March to May |
| Cottonwood and aspen | March to May |
| Maple (boxelder) | March to May |
| Birch and alder | April to May |
| Pine | May to June |
| Grass | May to July |
Season-by-season detail is on the Washington page.
Nearby calendars
Frost dates for Spokane come from the Spokane International Airport weather station's 30-year records. Season windows reviewed August 2026.