The Duluth year in pollen
Pollen seasons in Duluth: tree pollen March to June, grass May to July, and ragweed from mid-August until the first frost, around October 1.
Tree pollen
Grass
Ragweed
When does ragweed season end in Duluth?
Ragweed season in Duluth typically ends with the first frost, around October 1. Some years it comes as early as September 26, 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 13. Based on 30 years of NOAA frost records (1991–2020).
The rest of the Duluth 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 Minnesota page.
Nearby calendars
Frost dates for Duluth come from the Duluth weather station's 30-year records. Season windows reviewed August 2026.