The La Crosse year in pollen
Pollen seasons in La Crosse: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around October 17.
First frost lands around October 17 in La Crosse — about 7 days later than Wisconsin overall — which shifts when ragweed season ends here.
When does ragweed season end in La Crosse?
Ragweed season in La Crosse typically ends with the first frost, around October 17. Some years it comes as early as October 11, some as late as October 23.
A light frost around October 17 knocks the season down; the hard freeze that finishes it usually follows by October 28. Based on 30 years of NOAA frost records (1991–2020).
The rest of the La Crosse 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 La Crosse come from the La Crosse Municipal Airport weather station's 30-year records. Season windows reviewed August 2026.