The Cheyenne year in pollen
Pollen seasons in Cheyenne: tree pollen March to June, grass May to July, and ragweed from early August until the first frost, around October 1.
First frost lands around October 1 in Cheyenne — about 8 days later than Wyoming overall — which shifts when ragweed season ends here.
When does ragweed season end in Cheyenne?
Ragweed season in Cheyenne typically ends with the first frost, around October 1. Some years it comes as early as September 27, some as late as October 7.
A light frost around October 1 knocks the season down; the hard freeze that finishes it usually follows by October 11. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Cheyenne 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 Wyoming page.
Nearby calendars
Frost dates for Cheyenne come from the Cheyenne weather station's 30-year records. Season windows reviewed August 2026.