The Yakima year in pollen
Pollen seasons in Yakima: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around October 4.
Yakima's pollen year runs on a different clock than most of Washington — the seasons below follow Yakima's own climate, not the statewide picture.
When does ragweed season end in Yakima?
Ragweed season in Yakima typically ends with the first frost, around October 4. Some years it comes as early as September 30, some as late as October 9.
A light frost around October 4 knocks the season down; the hard freeze that finishes it usually follows by October 16. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Yakima 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 Yakima come from the Yakima Air Terminal weather station's 30-year records. Season windows reviewed August 2026.