The Eau Claire year in pollen
Pollen seasons in Eau Claire: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around October 4.
First frost lands around October 4 in Eau Claire — about 6 days earlier than Wisconsin overall — which shifts when ragweed season ends here.
When does ragweed season end in Eau Claire?
Ragweed season in Eau Claire typically ends with the first frost, around October 4. Some years it comes as early as September 29, some as late as October 10.
A light frost around October 4 knocks the season down; the hard freeze that finishes it usually follows by October 15. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Eau Claire pollen year
| Allergen | Typical season |
|---|---|
| Birch | April to May |
| Oak | April to June |
| Maple | March to May |
| Alder | March to April |
| Ash | April to May |
| Pine | May to June |
| Grass | May to July |
Season-by-season detail is on the Wisconsin page.
Nearby calendars
Frost dates for Eau Claire come from the Eau Claire Regional Airport weather station's 30-year records. Season windows reviewed August 2026.