The Idaho Falls year in pollen
Pollen seasons in Idaho Falls: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around September 20.
Tree pollen
Grass
Ragweed
When does ragweed season end in Idaho Falls?
Ragweed season in Idaho Falls typically ends with the first frost, around September 20. Some years it comes as early as September 12, some as late as September 27.
A light frost around September 20 knocks the season down; the hard freeze that finishes it usually follows by October 2. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Idaho Falls 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 Idaho page.
Nearby calendars
Frost dates for Idaho Falls come from the Idaho Falls Fanning Field weather station's 30-year records. Season windows reviewed August 2026.