The Des Moines year in pollen
Pollen seasons in Des Moines: tree pollen February to May, grass May to July, and ragweed from early August until the first frost, around October 20.
First frost lands around October 20 in Des Moines — about 9 days later than Iowa overall — which shifts when ragweed season ends here.
When does ragweed season end in Des Moines?
Ragweed season in Des Moines typically ends with the first frost, around October 20. Some years it comes as early as October 14, some as late as October 25.
A light frost around October 20 knocks the season down; the hard freeze that finishes it usually follows by October 30. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Des Moines pollen year
| Allergen | Typical season |
|---|---|
| Oak | April to May |
| Maple | March to April |
| Elm | February to April |
| Birch | April to May |
| Ash | April to May |
| Hickory and walnut | April to May |
| Grass | May to July |
Season-by-season detail is on the Iowa page.
Nearby calendars
Frost dates for Des Moines come from the Des Moines International Airport weather station's 30-year records. Season windows reviewed August 2026.